PHP TUTORIOL
Introduction OF
the PHP
If you want to learn the basics of PHP, then you've come to
the right place. The goal of this tutorial is to teach you the basics of PHP so
that you can:
- Customize PHP scripts that you download, so that they better fit your needs.
- Begin to understand the working model of PHP, so you may begin to design your own PHP projects.
- Give you a solid base in PHP, so as to make you more valuable in the eyes of future employers.
PHP stands for PHP Hypertext
Preprocessor.
PHP - What is it?
Taken directly from PHP's home, PHP.net, "PHP is an HTML-embedded scripting language. Much of its
syntax is borrowed from C, Java and Perl with a couple of unique PHP-specific
features thrown in. The goal of the language is to allow web developers to
write dynamically generated pages quickly."
This is generally a good definition
of PHP. However, it does contain a lot of terms you may not be used to. Another
way to think of PHP is a powerful, behind the scenes scripting language that
your visitors won't see!
When someone visits your PHP
webpage, your web server processes the PHP code. It then sees which parts it
needs to show to visitors(content and pictures) and hides the other stuff(file
operations, math calculations, etc.) then translates your PHP into HTML. After
the translation into HTML, it sends the webpage to your visitor's web browser.
PHP - What's it do?
It is also helpful to think of PHP
in terms of what it can do for you. PHP will allow you to:
- Reduce the time to create large websites.
- Create a customized user experience for visitors based on information that you have gathered from them.
- Open up thousands of possibilities for online tools. Check out PHP - HotScripts for examples of the great things that are possible with PHP.
- Allow creation of shopping carts for e-commerce websites.
What You Should Know
Before starting this tutorial it is
important that you have a basic understanding and experience in the following:
- HTML - Know the syntax and especially HTML Forms.
- Basic programming knowledge - This isn't required, but if you have any traditional programming experience it will make learning PHP a great deal easier.
Tutorial Overview
This tutorial is aimed at the PHP
novice and will teach you PHP from the ground up. If you want a drive-through
PHP tutorial this probably is not the right tutorial for you.
Remember, you should not try to plow
through this tutorial in one sitting. Read a couple lessons, take a break, then
do some more after the information has had some time to sink in.
PHP - Necessary Setup
To begin working with PHP you must first have access to either of the following:- A web hosting account that supports the use of PHP web pages and grants you access to MySQL databases. If you do not have a host, but are interested in signing up for one, we recommend that you first read our Web Host Guide to educate yourself about web hosting and avoid getting ripped off.
- Have PHP and MySQL installed on your own computer. Read this lesson thorougly for more information on installing PHP.
Although MySQL is not absolutely
necessary to use PHP, MySQL and PHP are wonderful complements to one another
and some topics covered in this tutorial will require that you have MySQL
access.
Installing PHP
For those who are experienced enough
to do this yourself, simply head over to PHP.net
- Downloads and download the most recent
version of PHP.
However, if you are like most of us,
you will most likely want to follow a guide to installing PHP onto your
computer. These guides are kindly provided by PHP.net based on the operating
system that you are using.
- PHP - Windows - Windows Installation Guide
- PHP - Mac - Mac Installation Guide
- PHP - Linux - Linux Installation Guide
Installing MySQL
As we mentioned before, MySQL is not
a requirement to use PHP, however they often go hand in hand.
Visit MySQL's MySQL Installation Guide
for help on installing MySQL.
PHP - Syntax
Before we talk about PHP's syntax, let us first define what syntax is referring to.- Syntax - The rules that must be followed to write properly structured code.
PHP Code:
<?php
?>
or the shorthand PHP tag that requires shorthand support to be enabled
on your server...
<?
?>If you are writing PHP scripts and plan on distributing them, we suggest that you use the standard form (which includes the ?php) rather than the shorthand form. This will ensure that your scripts will work, even when running on other servers with different settings.
How to Save Your PHP Pages
If you have PHP inserted into your HTML and want the web browser to interpret it correctly, then you must save the file with a .php extension, instead of the standard .html extension. So be sure to check that you are saving your files correctly. Instead of index.html, it should be index.php if there is PHP code in the file.Example Simple HTML & PHP Page
Below is an example of one of the easiest PHP and HTML page that you can create and still follow web standards.PHP and HTML Code:
<html>
<head>
<title>My First PHP Page</title>
</head>
<body>
<?php
echo "Hello World!";
?>
</body>
</html>
Display:
Hello World!
If you save this file (e.g. helloworld.php) and place it on PHP enabled
server and load it up in your web browser, then you should see "Hello
World!" displayed. If not, please check that you followed our example
correctly.We used the PHP command echo to write "Hello World!" and we will be talking in greater depth about how echo is special later on in this tutorial.
The Semicolon!
As you may or may not have noticed in the above example, there was a semicolon after the line of PHP code. The semicolon signifies the end of a PHP statement and should never be forgotten. For example, if we repeated our "Hello World!" code several times, then we would need to place a semicolon at the end of each statement.PHP and HTML Code:
<html>
<head>
<title>My First PHP Page</title>
</head>
<body>
<?php
echo "Hello World! ";
echo "Hello World! ";
echo "Hello World! ";
echo "Hello World! ";
echo "Hello World! ";
?>
</body>
</html>
Display:
Hello World! Hello World! Hello World! Hello World! Hello
World!
White Space
As with HTML, whitespace is ignored between PHP statements. This means it is OK to have one line of PHP code, then 20 lines of blank space before the next line of PHP code. You can also press tab to indent your code and the PHP interpreter will ignore those spaces as well.PHP and HTML Code:
<html>
<head>
<title>My First PHP Page</title>
</head>
<body>
<?php
echo "Hello World!";
echo "Hello World!";
?>
</body>
</html>
Display:
Hello World!Hello World!
This is perfectly legal PHP code.PHP - Variables
If you have never had any programming, Algebra, or scripting experience, then the concept of variables might be a new concept to you. A detailed explanation of variables is beyond the scope of this tutorial, but we've included a refresher crash course to guide you.A variable is a means of storing a value, such as text string "Hello World!" or the integer value 4. A variable can then be reused throughout your code, instead of having to type out the actual value over and over again. In PHP you define a variable with the following form:
- $variable_name = Value;
Note: Also, variable names are case-sensitive, so use the exact same capitalization when using a variable. The variables $a_number and $A_number are different variables in PHP's eyes.
A Quick Variable Example
Say that we wanted to store the values that we talked about in the above paragraph. How would we go about doing this? We would first want to make a variable name and then set that equal to the value we want. See our example below for the correct way to do this.PHP Code:
<?php
$hello = "Hello World!";
$a_number = 4;
$anotherNumber = 8;
?>
Note for programmers: PHP does not require variables to be declared before being initialized.
PHP Variable Naming Conventions
There are a few rules that you need to follow when choosing a name for your PHP variables.- PHP variables must start with a letter or underscore "_".
- PHP variables may only be comprised of alpha-numeric characters and underscores. a-z, A-Z, 0-9, or _ .
- Variables with more than one word should be separated with underscores. $my_variable
- Variables with more than one word can also be distinguished with capitalization. $myVariable
PHP - Echo
As you saw in the previous lesson, the PHP command echo is a means of outputting text to the web browser. Throughout your PHP career you will be using the echo command more than any other. So let's give it a solid perusal!Outputting a String
To output a string, like we have done in previous lessons, use PHP echo. You can place either a string variable or you can use quotes, like we do below, to create a string that the echo function will output.PHP Code:
<?php
$myString = "Hello!";
echo $myString;
echo "<h5>I love using PHP!</h5>";
?>
Display:
Hello!
I love using PHP!
In the above example we output "Hello!" without a hitch. The text we are outputting is being sent to the user in the form of a web page, so it is important that we use proper HTML syntax!In our second echo statement we use echo to write a valid Header 5 HTML statement. To do this we simply put the <h5> at the beginning of the string and closed it at the end of the string. Just because you're using PHP to make web pages does not mean you can forget about HTML syntax!
Careful When Echoing Quotes!
It is pretty cool that you can output HTML with PHP. However, you must be careful when using HTML code or any other string that includes quotes! Echo uses quotes to define the beginning and end of the string, so you must use one of the following tactics if your string contains quotations:- Don't use quotes inside your string
- Escape your quotes that are within the string with a backslash. To escape a quote just place a backslash directly before the quotation mark, i.e. \"
- Use single quotes (apostrophes) for quotes inside your string.
PHP Code:
<?php
// This won't work because of the quotes around specialH5!
echo "<h5 class="specialH5">I love using PHP!</h5>";
// OK because we escaped the quotes!
echo "<h5 class=\"specialH5\">I love using PHP!</h5>";
// OK because we used an apostrophe '
echo "<h5 class='specialH5'>I love using PHP!</h5>";
?>If you want to output a string that includes quotations, either use an apostrophe ( ' ) or escape the quotations by placing a backslash in front of it ( \" ). The backslash will tell PHP that you want the quotation to be used within the string and NOT to be used to end echo's string.
Echoing Variables
Echoing variables is very easy. The PHP developers put in some extra work to make the common task of echoing all variables nearly foolproof! No quotations are required, even if the variable does not hold a string. Below is the correct format for echoing a variable.PHP Code:
<?php
$my_string = "Hello Bob. My name is: ";
$my_number = 4;
$my_letter = a;
echo $my_string;
echo $my_number;
echo $my_letter;
?>
Display:
Hello Bob. My name is: 4a
Echoing Variables and Text Strings
You can also place variables inside of double-quoted strings (e.g. "string here and a $variable"). By putting a variable inside the quotes (" ") you are telling PHP that you want it to grab the string value of that variable and use it in the string. The example below shows an example of this cool feature.PHP Code:
<?php
$my_string = "Hello Bob. My name is: ";
echo "$my_string Bobettta <br />";
echo "Hi, I'm Bob. Who are you? $my_string <br />";
echo "Hi, I'm Bob. Who are you? $my_string Bobetta";
?>
Display:
Hello Bob. My name is: Bobetta
Hi, I'm Bob. Who are you? Hello Bob. My name is:
Hi, I'm Bob. Who are you? Hello Bob. My name is: Bobetta
By placing variables inside a string you can save yourself some time and
make your code easier to read, though it does take some getting used to.
Remember to use double-quotes, single-quotes will not grab the value of the
string. Single-quotes will just output the variable name to the string, like
)$my_string), rather than (Hello Bob. My name is: ).Hi, I'm Bob. Who are you? Hello Bob. My name is:
Hi, I'm Bob. Who are you? Hello Bob. My name is: Bobetta
PHP Echo - Not a Function
Echo is not a function, rather it is a language construct. When you use functions in PHP, they have a very particular form, which we will be going over later. For now, just know that echo is a special tool that you'll come to know and love!PHP - Strings
In the last lesson, PHPEcho, we used strings a bit, but didn't talk about them in depth. Throughout your PHP career you will be using strings a great deal, so it is important to have a basic understanding of PHP strings.PHP - String Creation
Before you can use a string you have to create it! A string can be used directly in a function or it can be stored in a variable. Below we create the exact same string twice: first storing it into a variable and in the second case we send the string directly to echo.PHP Code:
$my_string = "Tizag - Unlock your potential!";
echo "Tizag - Unlock your potential!";
echo $my_string;In the above example the first string will be stored into the variable $my_string, while the second string will be used in the echo and not be stored. Remember to save your strings into variables if you plan on using them more than once! Below is the output from our example code. They look identical just as we thought.
Display:
Tizag - Unlock your potential! Tizag - Unlock your
potential!
PHP - String Creation Single Quotes
Thus far we have created strings using double-quotes, but it is just as correct to create a string using single-quotes, otherwise known as apostrophes.PHP Code:
$my_string = 'Tizag - Unlock your potential!';
echo 'Tizag - Unlock your potential!';
echo $my_string;If you want to use a single-quote within the string you have to escape the single-quote with a backslash \ . Like this: \' !
PHP Code:
echo 'Tizag - It\'s Neat!';
PHP - String Creation Double-Quotes
We have used double-quotes and will continue to use them as the primary method for forming strings. Double-quotes allow for many special escaped characters to be used that you cannot do with a single-quote string. Once again, a backslash is used to escape a character.PHP Code:
$newline = "A newline is \n";
$return = "A carriage return is \r";
$tab = "A tab is \t";
$dollar = "A dollar sign is \$";
$doublequote = "A double-quote is \"";Note: If you try to escape a character that doesn't need to be, such as an apostrophe, then the backslash will show up when you output the string.
These escaped characters are not very useful for outputting to a web page because HTML ignore extra white space. A tab, newline, and carriage return are all examples of extra (ignorable) white space. However, when writing to a file that may be read by human eyes these escaped characters are a valuable tool!
PHP - String Creation Heredoc
The two methods above are the traditional way to create strings in most programming languages. PHP introduces a more robust string creation tool called heredoc that lets the programmer create multi-line strings without using quotations. However, creating a string using heredoc is more difficult and can lead to problems if you do not properly code your string! Here's how to do it:PHP Code:
$my_string = <<<TEST
Tizag.com
Webmaster Tutorials
Unlock your potential!
TEST;
echo $my_string;There are a few very important things to remember when using heredoc.
- Use <<< and some identifier that you choose to begin the heredoc. In this example we chose TEST as our identifier.
- Repeat the identifier followed by a semicolon to end the heredoc string creation. In this example that was TEST;
- The closing sequence TEST; must occur on a line by itself and cannot be indented!
Display:
Tizag.com Webmaster Tutorials Unlock your potential!
Once again, take great care in following the heredoc creation guidelines to
avoid any headaches.PHP - Operators
In all programming languages, operators are used to manipulate or perform operations on variables and values. You have already seen the string concatenation operator "." in the Echo Lesson and the assignment operator "=" in pretty much every PHP example so far.There are many operators used in PHP, so we have separated them into the following categories to make it easier to learn them all.
- Assignment Operators
- Arithmetic Operators
- Comparison Operators
- String Operators
- Combination Arithmetic & Assignment Operators
Assignment Operators
Assignment operators are used to set a variable equal to a value or set a variable to another variable's value. Such an assignment of value is done with the "=", or equal character. Example:- $my_var = 4;
- $another_var = $my_var;
Arithmetic Operators
|
Operator
|
English
|
Example
|
|
+
|
Addition
|
2 + 4
|
|
-
|
Subtraction
|
6 - 2
|
|
*
|
Multiplication
|
5 * 3
|
|
/
|
Division
|
15 / 3
|
|
%
|
Modulus
|
43 % 10
|
PHP Code:
$addition = 2 + 4;
$subtraction = 6 - 2;
$multiplication = 5 * 3;
$division = 15 / 3;
$modulus = 5 % 2;
echo "Perform addition: 2 + 4 = ".$addition."<br />";
echo "Perform subtraction: 6 - 2 = ".$subtraction."<br />";
echo "Perform multiplication: 5 * 3 = ".$multiplication."<br />";
echo "Perform division: 15 / 3 = ".$division."<br />";
echo "Perform modulus: 5 % 2 = " . $modulus
. ". Modulus is the remainder after the division operation has been performed.
In this case it was 5 / 2, which has a remainder of 1.";
Display:
Perform addition: 2 + 4 = 6
Perform subtraction: 6 - 2 = 4
Perform multiplication: 5 * 3 = 15
Perform division: 15 / 3 = 5
Perform modulus: 5 % 2 = 1. Modulus is the remainder after the division operation has been performed. In this case it was 5 / 2, which has a remainder of 1.
Perform subtraction: 6 - 2 = 4
Perform multiplication: 5 * 3 = 15
Perform division: 15 / 3 = 5
Perform modulus: 5 % 2 = 1. Modulus is the remainder after the division operation has been performed. In this case it was 5 / 2, which has a remainder of 1.
Comparison Operators
Comparisons are used to check the relationship between variables and/or values. If you would like to see a simple example of a comparison operator in action, check out our IfStatement Lesson. Comparison operators are used inside conditional statements and evaluate to either true or false. Here are the most important comparison operators of PHP.Assume: $x = 4 and $y = 5;
|
Operator
|
English
|
Example
|
Result
|
|
==
|
Equal To
|
$x == $y
|
false
|
|
!=
|
Not Equal To
|
$x != $y
|
true
|
|
<
|
Less Than
|
$x < $y
|
true
|
|
>
|
Greater Than
|
$x > $y
|
false
|
|
<=
|
Less Than or Equal To
|
$x <= $y
|
true
|
|
>=
|
Greater Than or Equal To
|
$x >= $y
|
false
|
String Operators
As we have already seen in the EchoLesson, the period "." is used to add two strings together, or more technically, the period is the concatenation operator for strings.PHP Code:
$a_string = "Hello";
$another_string = " Billy";
$new_string = $a_string . $another_string;
echo $new_string . "!";
Display:
Hello Billy!
Combination Arithmetic & Assignment Operators
In programming it is a very common task to have to increment a variable by some fixed amount. The most common example of this is a counter. Say you want to increment a counter by 1, you would have:- $counter = $counter + 1;
- $counter += 1;
|
Operator
|
English
|
Example
|
Equivalent
Operation
|
|
+=
|
Plus Equals
|
$x += 2;
|
$x = $x + 2;
|
|
-=
|
Minus Equals
|
$x -= 4;
|
$x = $x - 4;
|
|
*=
|
Multiply Equals
|
$x *= 3;
|
$x = $x * 3;
|
|
/=
|
Divide Equals
|
$x /= 2;
|
$x = $x / 2;
|
|
%=
|
Modulo Equals
|
$x %= 5;
|
$x = $x % 5;
|
|
.=
|
Concatenate Equals
|
$my_str.="hello";
|
$my_str = $my_str . "hello";
|
Pre/Post-Increment & Pre/Post-Decrement
This may seem a bit absurd, but there is even a shorter shorthand for the common task of adding 1 or subtracting 1 from a variable. To add one to a variable or "increment" use the "++" operator:- $x++; Which is equivalent to $x += 1; or $x = $x + 1;
- $x--; Which is equivalent to $x -= 1; or $x = $x - 1;
PHP Code:
$x = 4;
echo "The value of x with post-plusplus = " . $x++;
echo "<br /> The value of x after the post-plusplus is " . $x;
$x = 4;
echo "<br />The value of x with with pre-plusplus = " . ++$x;
echo "<br /> The value of x after the pre-plusplus is " . $x;
Display:
The value of x with post-plusplus = 4
The value of x after the post-plusplus is = 5
The value of x with with pre-plusplus = 5
The value of x after the pre-plusplus is = 5
As you can see the value of $x++ is not reflected in the echoed text because
the variable is not incremented until after the line of code is executed.
However, with the pre-increment "++$x" the variable does reflect the
addition immediately.The value of x after the post-plusplus is = 5
The value of x with with pre-plusplus = 5
The value of x after the pre-plusplus is = 5
In HTML a comment's main purpose is to serve as a note to you, the web developer or to others who may view your website's source code. However, PHP's comments are different in that they will not be displayed to your visitors. The only way to view PHP comments is to open the PHP file for editing. This makes PHP comments only useful to PHP programmers.
In case you forgot what an HTML comment looked like, see our example below.
HTML Code:
<!-- This is an HTML Comment -->
PHP Comment Syntax: Single Line Comment
While there is only one type of comment in HTML, PHP has two types. The first type we will discuss is the single line comment. The single line comment tells the interpreter to ignore everything that occurs on that line to the right of the comment. To do a single line comment type "//" or "#" and all text to the right will be ignored by PHP interpreter.PHP Code:
<?php
echo "Hello World!"; // This will print out Hello World!
echo "<br />Psst...You can't see my PHP comments!"; // echo "nothing";
// echo "My name is Humperdinkle!";
# echo "I don't do anything either";
?>
Display:
Hello World!
Psst...You can't see my PHP comments!
Notice that a couple of our echo statements were not evaluated because we
commented them out with the single line comment. This type of line commenting
is often used for quick notes about complex and confusing code or to
temporarily remove a line of PHP code.Psst...You can't see my PHP comments!
PHP Comment Syntax: Multiple Line Comment
Similiar to the HTML comment, the multi-line PHP comment can be used to comment out large blocks of code or writing multiple line comments. The multiple line PHP comment begins with " /* " and ends with " */ ".PHP Code:
<?php
/* This Echo statement will print out my message to the
the place in which I reside on. In other words, the World. */
echo "Hello World!";
/* echo "My name is Humperdinkle!";
echo "No way! My name is Uber PHP Programmer!";
*/
?>
Display:
Hello World!
Good Commenting Practices
One of the best commenting practices that I can recommend to new PHP programmers is....USE THEM!! So many people write complex PHP code and are either too lazy to write good comments or believe the commenting is not needed. However, do you really believe that you will remember exactly what you were thinking when looking at this code a year or more down the road?Let the comments permeate your code and you will be a happier PHPer in the future. Use single line comments for quick notes about a tricky part in your code and use multiple line comments when you need to describe something in greater depth than a simple note.
PHP Include
Without understanding much about the details of PHP, you can save yourself a great deal of time with the use of the PHP include command. include takes a file name and simply inserts that file's contents into the script that issued the include command.Why is this a cool thing? Well, first of all, this means that you can type up a common header or menu file that you want all your web pages to include. When you add a new page to your site, instead of having to update the links on several web pages, you can simply change the Menu file.
An Include Example
Say we wanted to create a common menu file that all our pages will use. A common practice for naming files that are to be included is to use the ".php" extension. Since we want to create a common menu let's save it as "menu.php".menu.php Code:
<html>
<body>
<a href="http://www.example.com/index.php">Home</a> -
<a href="http://www.example.com/about.php">About Us</a> -
<a href="http://www.example.com/links.php">Links</a> -
<a href="http://www.example.com/contact.php">Contact Us</a> <br />Save the above file as "menu.php". Now create a new file, "index.php" in the same directory as "menu.php". Here we will take advantage of the include command to add our common menu.
index.php Code:
<?php include("menu.php"); ?>
<p>This is my home page that uses a common menu to save me time when I add
new pages to my website!</p>
</body>
</html>
Display:
This is my home page that uses a common menu to save me time when I add new pages to my website!And we would do the same thing for "about.php", "links.php", and "contact.php". Just think how terrible it would be if you had 15 or more pages with a common menu and you decided to add another web page to that site. You would have to go in and manually edit every single file to add this new page, but with include files you simply have to change "menu.php" and all your problems are solved. Avoid such troublesome occasions with a simple include file.
What do Visitors See?
If we were to use the include command to insert a menu on each of our web pages, what would the visitor see if they viewed the source of "index.php"? Well, because the include command is pretty much the same as copying and pasting, the visitors would see:View Source of index.php to a Visitor:
<html>
<body>
<a href="index.php">Home</a> -
<a href="about.php">About Us</a> -
<a href="links.php">Links</a> -
<a href="contact.php">Contact Us</a> <br />
<p>This is my home page that uses a common menu to save me time when I add
new pages to my website!</p>
</body>
</html>The visitor would actually see all the HTML code as one long line of HTML code, because we have not inserted any new line characters. We did some formatting above to make it easier to read. We will be discussing new line characters later.
Include Recap
The include command simply takes all the text that exists in the specified file and copies it into the file that uses the include command. Include is quite useful when you want to include the same PHP, HTML, or text segment on multiple pages of a website. The include command is used widely by PHP web developers. Like PHPEcho, include is not a function, but a language construct.The next lesson will talk about a slight variation of the include command: require. It is often best to use the require command instead of the include command in your PHP Code. Read the next lesson to find out why!
PHP Require
Just like the previous lesson, the require command is used to include a file into your PHP code. However there is one huge difference between the two commands, though it might not seem that big of a deal.Require vs Include
When you include a file with the include command and PHP cannot find it you will see an error message like the following:PHP Code:
<?php
include("noFileExistsHere.php");
echo "Hello World!";
?>
Display:
Warning: main(noFileExistsHere.php): failed to open
stream: No such file or directory in /home/websiteName/FolderName/tizagScript.php
on line 2 Warning: main(): Failed opening
'noFileExistsHere.php' for inclusion
(include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/websiteName/FolderName/tizagScript.php
on line 2
Hello World!
Notice that our echo statement is still executed, this is because a Warning
does not prevent our PHP script from running. On the other hand, if we did the
same example but used the require statement we would get something like the
following example.Hello World!
PHP Code:
<?php
require("noFileExistsHere.php");
echo "Hello World!";
?>
Display:
Warning: main(noFileExistsHere.php): failed to open
stream: No such file or directory in /home/websiteName/FolderName/tizagScript.php
on line 2
Fatal error: main(): Failed opening required 'noFileExistsHere.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/websiteName/FolderName/tizagScript.php on line 2
The echo statement was not executed because our script execution died after
the require command returned a fatal error! We recommend that you use
require instead of include because your scripts should not be executing if
necessary files are missing or misnamed.Fatal error: main(): Failed opening required 'noFileExistsHere.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/websiteName/FolderName/tizagScript.php on line 2
The If Statement
The PHP if statement is very similar to other programming languages use of the if statement, but for those who are not familiar with it, picture the following:Think about the decisions you make before you go to sleep. If you have something to do the next day, say go to work, school, or an appointment, then you will set your alarm clock to wake you up. Otherwise, you will sleep in as long as you like!
This simple kind of if/then statement is very common in every day life and also appears in programming quite often. Whenever you want to make a decision given that something is true (you have something to do tomorrow) and be sure that you take the appropriate action, you are using an if/then relationship.
The PHP If Statement
The if statement is necessary for most programming, thus it is important in PHP. Imagine that on January 1st you want to print out "Happy New Year!" at the top of your personal web page. With the use of PHP if statements you could have this process automated, months in advance, occuring every year on January 1st.This idea of planning for future events is something you would never have had the opportunity of doing if you had just stuck with HTML.
If Statement Example
The "Happy New Year" example would be a little difficult for you to do right now, so let us instead start off with the basics of the if statement. The PHP if statement tests to see if a value is true, and if it is a segment of code will be executed. See the example below for the form of a PHP if statement.PHP Code:
$my_name = "someguy";
if ( $my_name == "someguy" ) {
echo "Your name is someguy!<br />";
}
echo "Welcome to my homepage!";
Display:
Your name is someguy!
Welcome to my homepage!
Did you get that we were comparing the variable $my_name with
"someguy" to see if they were equal? In PHP you use the double equal
sign (==) to compare values. Additionally, notice that because the if statement
turned out to be true, the code segment was executed, printing out "Your
name is someguy!". Let's go a bit more in-depth into this example to iron
out the details.Welcome to my homepage!
- We first set the variable $my_name equal to "someguy".
- We next used a PHP if statement to check if the value contained in the variable $my_name was equal to "someguy"
- The comparison between $my_name and "someguy" was done with a double equal sign "==", not a single equals"="! A single equals is for assigning a value to a variable, while a double equals is for checking if things are equal.
- Translated into english the PHP statement ( $my_name == "someguy" ) is ( $my_name is equal to "someguy" ).
- $my_name is indeed equal to "someguy" so the echo statement is executed.
A False If Statement
Let us now see what happens when a PHP if statement is not true, in other words, false. Say that we changed the above example to:PHP Code:
$my_name = "anotherguy";
if ( $my_name == "someguy" ) {
echo "Your name is someguy!<br />";
}
echo "Welcome to my homepage!";
Display:
Welcome to my homepage!
Here the variable contained the value "anotherguy", which is not
equal to "someguy". The if statement evaluated to false, so
the code segment of the if statement was not executed. When used properly, the if
statement is a powerful tool to have in your programming arsenal!If/Else Conditional Statment
Has someone ever told you, "if you work hard, then you will succeed"? And what happens if you do not work hard? Well, you fail! This is an example of an if/else conditional statement.- If you work hard then you will succeed.
- Else, if you do not work hard, then you will fail.
Someone comes to your website and you want to ask this visitor her name if it is her first time coming to your site. With an if statement this is easy. Simply have a conditional statement to check, "are you visiting for the first time". If the condition is true, then take them to the "Insert Your Name" page, else let her view the website as normal because you have already asked her for her name in the past.
If/Else an Example
Using these conditional statements can add a new layers of "cool" to your website. Here's the basic form of an if/else statement in PHP.PHP Code:
$number_three = 3;
if ( $number_three == 3 ) {
echo "The if statement evaluated to true";
} else {
echo "The if statement evaluated to false";
}
Display:
The if statement evaluated to true
This is a lot to digest in one sitting, so let us step through the code,
line by line.- We first made a PHP variable called $number_three and set it equal to 3.
- In this example we compared a variable to an integer value. To do such a comparison we use "==", which in English means "Is Equal To".
- $number_three is indeed Equal To 3 and so this statement will evaluate to true.
- All code that is contained between the opening curly brace "{" that follows the if statement and the closing curly brace "}" will be executed when the if statement is true.
- The code contained within the else segment will not used.
Execute Else Code with False
On the other hand, if the if statement was false, then the code contained in the else segment would have been executed. Note that the code within the if and else cannot both be executed, as the if statement cannot evaluate to both true and false at one time! Here is what would happen if we changed to $number_three to anything besides the number 3.PHP Code:
$number_three = 421;
if ( $number_three == 3 ) {
echo "The if statement evaluated to true";
} else {
echo "The if statement evaluated to false";
}
Display:
The if statement evaluated to false
The variable was set to 421, which is not equal to 3 and the if statement
was false. As you can see, the code segment contained within the else was used
in this case.PHP - Elseif
An if/else statement is great if you only need to check for one condition. However, what would you do if you wanted to check if your $employee variable was the company owner Bob, the Vice President Ms. Tanner, or a regular employee? To check for these different conditions you would need the elseif statement.PHP - Elseif What is it?
An if statement is made up of the keyword "if" and a conditional statement (i.e. $name == "Ted"). Just like an if statement, an elseif statement also contains a conditional statement, but it must be preceded by an if statement. You cannot have an elseif statement without first having an if statement.When PHP evaluates your If...elseif...else statement it will first see if the If statement is true. If that tests comes out false it will then check the first elseif statement. If that is false it will either check the next elseif statement, or if there are no more elseif statements, it will evaluate the else segment, if one exists (I don't think I've ever used the word "if" so much in my entire life!). Let's take a look at a real world example.
PHP - Using Elseif with If...Else
Let's start out with the base case. Imagine we have a simpler version of the problem described above. We simply want to find out if the employee is the Vice President Ms. Tanner. We only need an if else statement for this part of the example.PHP Code:
$employee = "Bob";
if($employee == "Ms. Tanner"){
echo "Hello Ma'am";
} else {
echo "Morning";
}Now, if we wanted to also check to see if the big boss Bob was the employee we need to insert an elseif clause.
PHP Code:
$employee = "Bob";
if($employee == "Ms. Tanner"){
echo "Hello Ma'am";
} elseif($employee == "Bob"){
echo "Good Morning Sir!";
}else {
echo "Morning";
}
Display:
Good Morning Sir!
PHP first checked to see if $employee was equal to "Ms.
Tanner", which evaluated to false. Next, PHP checked the first elseif
statement. $employee did in fact equal "Bob" so the phrase
"Good Morning Sir!" was printed out. If we wanted to check for more
employee names we could insert more elseif statements!Remember that an elseif statement cannot be used unless it is preceded by an if statement!
PHP Switch Statement
In the previous lessons we covered the various elements that make up an If Statement in PHP. However, there are times when an if statement is not the most efficient way to check for certain conditions.For example we might have a variable that stores travel destinations and you want to pack according to this destination variable. In this example you might have 20 different locations that you would have to check with a nasty long block of If/ElseIf/ElseIf/ElseIf/... statements. This doesn't sound like much fun to code, let's see if we can do something different.
PHP Switch Statement: Speedy Checking
With the use of the switch statement you can check for all these conditions at once, and the great thing is that it is actually more efficient programming to do this. A true win-win situation!The way the Switch statement works is it takes a single variable as input and then checks it against all the different cases you set up for that switch statement. Instead of having to check that variable one at a time, as it goes through a bunch of If Statements, the Switch statement only has to check one time.
PHP Switch Statement Example
In our example the single variable will be $destination and the cases will be: Las Vegas, Amsterdam, Egypt, Tokyo, and the Caribbean Islands.PHP Code:
$destination = "Tokyo";
echo "Traveling to $destination<br />";
switch ($destination){
case "Las Vegas":
echo "Bring an extra $500";
break;
case "Amsterdam":
echo "Bring an open mind";
break;
case "Egypt":
echo "Bring 15 bottles of SPF 50 Sunscreen";
break;
case "Tokyo":
echo "Bring lots of money";
break;
case "Caribbean Islands":
echo "Bring a swimsuit";
break;
}
Display:
Traveling to Tokyo
Bring lots of money
The value of $destination was Tokyo, so when PHP performed the switch
operating on $destination in immediately did a search for a case with
the value of "Tokyo". It found it and proceeded to execute the code
that existed within that segment.Bring lots of money
You might have noticed how each case contains a break; at the end of its code area. This break prevents the other cases from being executed. If the above example did not have any break statements then all the cases that follow Tokyo would have been executed as well. Use this knowledge to enhance the power of your switch statements!
The form of the switch statement is rather unique, so spend some time reviewing it before moving on. Note: Beginning programmers should always include the break; to avoid any unnecessary confusion.
PHP Switch Statement: Default Case
You may have noticed the lack of a place for code when the variable doesn't match our condition. The if statement has the else clause and the switch statement has the default case.It's usually a good idea to always include the default case in all your switch statements. Below is a variation of our example that will result in none of the cases being used causing our switch statement to fall back and use the default case. Note: the word case does not appear before the word default, as default is a special keyword!
PHP Code:
$destination = "New York";
echo "Traveling to $destination<br />";
switch ($destination){
case "Las Vegas":
echo "Bring an extra $500";
break;
case "Amsterdam":
echo "Bring an open mind";
break;
case "Egypt":
echo "Bring 15 bottles of SPF 50 Sunscreen";
break;
case "Tokyo":
echo "Bring lots of money";
break;
case "Caribbean Islands":
echo "Bring a swimsuit";
break;
default:
echo "Bring lots of underwear!";
break;
}
Display:
Traveling to New York
Bring lots of underwear!
Bring lots of underwear!
Using PHP With HTML Forms
It is time to apply the knowledge you have obtained thus far and put it to real use. A very common application of PHP is to have an HTML form gather information from a website's visitor and then use PHP to do process that information. In this lesson we will simulate a small business's website that is implementing a very simple order form.Imagine we are an art supply store that sells brushes, paint, and erasers. To gather order information from our prospective customers we will have to make a page with an HTML form to gather the customer's order.
Note: This is an oversimplified example to educate you how to use PHP to process HTML form information. This example is not intended nor advised to be used on a real business website.
Creating the HTML Form
If you need a refresher on how to properly make an HTML form, check out the HTML Form Lesson before continuing on.We first create an HTML form that will let our customer choose what they would like to purchase. This file should be saved as "order.html"
.
order.html Code:
<html><body>
<h4>Tizag Art Supply Order Form</h4>
<form>
<select>
<option>Paint</option>
<option>Brushes</option>
<option>Erasers</option>
</select>
Quantity: <input type="text" />
<input type="submit" />
</form>
</body></html>
Display:
Tizag Art Supply Order Form
Remember to review HTMLForms if you do not understand any of the above HTML code. Next we must alter our HTML form to specify the PHP page we wish to send this information to. Also, we set the method to "post".order.html Code:
<html><body>
<h4>Tizag Art Supply Order Form</h4>
<form action="process.php" method="post">
<select name="item">
<option>Paint</option>
<option>Brushes</option>
<option>Erasers</option>
</select>
Quantity: <input name="quantity" type="text" />
<input type="submit" />
</form>
</body></html>Now that our "order.html" is complete, let us continue on and create the "process.php" file which will process the HTML form information.
PHP Form Processor
We want to get the "item" and "quantity" inputs that we have specified in our HTML form. Using an associative array (this term is explained in the array lesson), we can get this information from the $_POST associative array.The proper way to get this information would be to create two new variables, $item and $quantity and set them equal to the values that have been "posted". The name of this file is "process.php".
process.php Code:
<html><body>
<?php
$quantity = $_POST['quantity'];
$item = $_POST['item'];
echo "You ordered ". $quantity . " " . $item . ".<br />";
echo "Thank you for ordering from Tizag Art Supplies!";
?>
</body></html>As you probably noticed, the name in $_POST['name'] corresponds to the name that we specified in our HTML form.
Now try uploading the "order.html" and "process.php" files to a PHP enabled server and test them out. If someone selected the item brushes and specified a quantity of 6, then the following would be displayed on "process.php":
process.php Code:
You ordered 6 brushes.
Thank you for ordering from Tizag Art Supplies!
PHP & HTML Form Review
A lot of things were going on in this example. Let us step through it to be sure you understand what was going on.- We first created an HTML form "order.html" that had two input fields specified, "item" and "quantity".
- We added two attributes to the form tag to point to "process.php" and set the method to "post".
- We had "process.php" get the information that was posted by setting new variables equal to the values in the $_POST associative array.
- We used the PHP echo function to output the customers order.
PHP - Functions
A function is just a name we give to a block of code that can be executed whenever we need it. This might not seem like that big of an idea, but believe me, when you understand and use functions you will be able to save a ton of time and write code that is much more readable!For example, you might have a company motto that you have to display at least once on every webpage. If you don't, then you get fired! Well, being the savvy PHP programmer you are, you think to yourself, "this sounds like a situation where I might need functions."
Tip: Although functions are often thought of as an advanced topic for beginning programmers to learn, if you take it slow and stick with it, functions can be just minor speedbump in your programming career. So don't give up if functions confuse you at first!
Creating Your First PHP Function
When you create a function, you first need to give it a name, like myCompanyMotto. It's with this function name that you will be able to call upon your function, so make it easy to type and understand.The actual syntax for creating a function is pretty self-explanatory, but you can be the judge of that. First, you must tell PHP that you want to create a function. You do this by typing the keyword function followed by your function name and some other stuff (which we'll talk about later).
Here is how you would make a function called myCompanyMotto. Note: We still have to fill in the code for myCompanyMotto.
PHP Code:
<?php
function myCompanyMotto(){
}
?>Note: Your function name can start with a letter or underscore "_", but not a number!
With a properly formatted function in place, we can now fill in the code that we want our function to execute. Do you see the curly braces in the above example "{ }"? These braces define where our function's code goes. The opening curly brace "{" tells php that the function's code is starting and a closing curly brace "}" tells PHP that our function is done!
We want our function to print out the company motto each time it's called, so that sounds like it's a job for the echo command!
PHP Code:
<?php
function myCompanyMotto(){
echo "We deliver quantity, not quality!<br />";
}
?>That's it! You have written your first PHP function from scratch! Notice that the code that appears within a function is just the same as any other PHP code.
Using Your PHP Function
Now that you have completed coding your PHP function, it's time to put it through a test run. Below is a simple PHP script. Let's do two things: add the function code to it and use the function twice.PHP Code:
<?php
echo "Welcome to Tizag.com <br />";
echo "Well, thanks for stopping by! <br />";
echo "and remember... <br />";
?>
PHP Code with Function:
<?php
function myCompanyMotto(){
echo "We deliver quantity, not quality!<br />";
}
echo "Welcome to Tizag.com <br />";
myCompanyMotto();
echo "Well, thanks for stopping by! <br />";
echo "and remember... <br />";
myCompanyMotto();
?>
Display:
Welcome to Tizag.com
We deliver quantity, not quality!
Well, thanks for stopping by!
and remember...
We deliver quantity, not quality!
Although this was a simple example, it's important to understand that there
is a lot going on and there are a lot of areas to make errors. When you are
creating a function, follow these simple guidelines:We deliver quantity, not quality!
Well, thanks for stopping by!
and remember...
We deliver quantity, not quality!
- Always start your function with the keyword function
- Remember that your function's code must be between the "{" and the "}"
- When you are using your function, be sure you spell the function name correctly
- Don't give up!
PHP Functions - Parameters
Another useful thing about functions is that you can send them information that the function can then use. Our first function myCompanyMotto isn't all that useful because all it does, and ever will do, is print out a single, unchanging string.However, if we were to use parameters, then we would be able to add some extra functionality! A parameter appears with the parentheses "( )" and looks just like a normal PHP variable. Let's create a new function that creates a custom greeting based off of a person's name.
Our parameter will be the person's name and our function will concatenate this name onto a greeting string. Here's what the code would look like.
PHP Code with Function:
<?php
function myGreeting($firstName){
echo "Hello there ". $firstName . "!<br />";
}
?>When we use our myGreeting function we have to send it a string containing someone's name, otherwise it will break. When you add parameters, you also add more responsibility to you, the programmer! Let's call our new function a few times with some common first names.
PHP Code:
<?php
function myGreeting($firstName){
echo "Hello there ". $firstName . "!<br />";
}
myGreeting("Jack");
myGreeting("Ahmed");
myGreeting("Julie");
myGreeting("Charles");
?>
Display:
Hello there Jack!
Hello there Ahmed!
Hello there Julie!
Hello there Charles!
It is also possible to have multiple parameters in a function. To separate
multiple parameters PHP uses a comma ",". Let's modify our function
to also include last names.Hello there Ahmed!
Hello there Julie!
Hello there Charles!
PHP Code:
<?php
function myGreeting($firstName, $lastName){
echo "Hello there ". $firstName ." ". $lastName ."!<br />";
}
myGreeting("Jack", "Black");
myGreeting("Ahmed", "Zewail");
myGreeting("Julie", "Roberts");
myGreeting("Charles", "Schwab");
?>
Display:
Hello there Jack Black!
Hello there Ahmed Zewail!
Hello there Julie Roberts!
Hello there Charles Schwab!
Hello there Ahmed Zewail!
Hello there Julie Roberts!
Hello there Charles Schwab!
PHP Functions - Returning Values
Besides being able to pass functions information, you can also have them return a value. However, a function can only return one thing, although that thing can be any integer, float, array, string, etc. that you choose!How does it return a value though? Well, when the function is used and finishes executing, it sort of changes from being a function name into being a value. To capture this value you can set a variable equal to the function. Something like:
- $myVar = somefunction();
PHP Code:
<?php
function mySum($numX, $numY){
$total = $numX + $numY;
return $total;
}
$myNumber = 0;
echo "Before the function, myNumber = ". $myNumber ."<br />";
$myNumber = mySum(3, 4); // Store the result of mySum in $myNumber
echo "After the function, myNumber = " . $myNumber ."<br />";
?>
Display:
Before the function, myNumber = 0
After the function, myNumber = 7
When we first print out the value of $myNumber it is still set to the
original value of 0. However, when we set $myNumber equal to the function mySum,
$myNumber is set equal to mySum's result. In this case, the result was 3 + 4 =
7, which was successfully stored into $myNumber and displayed in the second
echo statement!After the function, myNumber = 7
PHP Functions - Practice Makes Perfect
If you are new to programming, then this lesson might or might not seem like overkill. If you are having a hard time understanding lessons, the best piece of advice would be to do your best the first time, then be sure to come back tomorrow and next week and see if it makes anymore sense. Chances are, after going through this tutorial more than once, with breaks in between, this topic will be mastered.PHP Array
An array is a data structure that stores one or more values in a single value. For experienced programmers it is important to note that PHP's arrays are actually maps (each key is mapped to a value).PHP - A Numerically Indexed Array
If this is your first time seeing an array, then you may not quite understand the concept of an array. Imagine that you own a business and you want to store the names of all your employees in a PHP variable. How would you go about this?It wouldn't make much sense to have to store each name in its own variable. Instead, it would be nice to store all the employee names inside of a single variable. This can be done, and we show you how below.
PHP Code:
$employee_array[0] = "Bob";
$employee_array[1] = "Sally";
$employee_array[2] = "Charlie";
$employee_array[3] = "Clare";In the above example we made use of the key / value structure of an array. The keys were the numbers we specified in the array and the values were the names of the employees. Each key of an array represents a value that we can manipulate and reference. The general form for setting the key of an array equal to a value is:
- $array[key] = value;
Note: As you may have noticed from the above code example, an array's keys start from 0 and not 1. This is a very common problem for many new programmers who are used to counting from 1 and lead to "off by 1" errors. This is just something that will take experience before you are fully comfortable with it.
PHP Code:
echo "Two of my employees are "
. $employee_array[0] . " & " . $employee_array[1];
echo "<br />Two more employees of mine are "
. $employee_array[2] . " & " . $employee_array[3];
Display:
Two of my employees are Bob & Sally
Two more employees of mine are Charlie & Clare
PHP arrays are quite useful when used in conjunction with loops, which we
will talk about in a later lesson. Above we showed an example of an array that
made use of integers for the keys (a numerically indexed array).
However, you can also specify a string as the key, which is referred to
as an associative array.Two more employees of mine are Charlie & Clare
PHP - Associative Arrays
In an associative array a key is associated with a value. If you wanted to store the salaries of your employees in an array, a numerically indexed array would not be the best choice. Instead, we could use the employees names as the keys in our associative array, and the value would be their respective salary.PHP Code:
$salaries["Bob"] = 2000;
$salaries["Sally"] = 4000;
$salaries["Charlie"] = 600;
$salaries["Clare"] = 0;
echo "Bob is being paid - $" . $salaries["Bob"] . "<br />";
echo "Sally is being paid - $" . $salaries["Sally"] . "<br />";
echo "Charlie is being paid - $" . $salaries["Charlie"] . "<br />";
echo "Clare is being paid - $" . $salaries["Clare"];
Display:
Bob is being paid - $2000
Sally is being paid - $4000
Charlie is being paid - $600
Clare is being paid - $0
Once again, the usefulness of arrays will become more apparent once you have
knowledge of for
and while loops.Sally is being paid - $4000
Charlie is being paid - $600
Clare is being paid - $0
PHP - While Loop
Repetitive tasks are always a burden to us. Deleting spam email, sealing 50 envelopes, and going to work are all examples of tasks that are repeated. The nice thing about programming is that you can avoid such repetitive tasks with a little bit of extra thinking. Most often these repetitive tasks are conquered in the loop.The idea of a loop is to do something over and over again until the task has been completed. Before we show a real example of when you might need one, let's go over the structure of the PHP while loop.
Simple While Loop Example
The function of the while loop is to do a task over and over as long as the specified conditional statement is true. This logical check is the same as the one that appears in a PHP if statement to determine if it is true or false. Here is the basic structure of a PHP while loop:Pseudo PHP Code:
while ( conditional statement is true){
//do this code;
}This isn't valid PHP code, but it displays how the while loop is structured. Here is the break down of how a while loop functions when your script is executing:
- The conditional statement is checked. If it is true, then (2) occurs. If it is false, then (4) occurs.
- The code within the while loop is executed.
- The process starts again at (1). Effectively "looping" back.
- If the conditional statement is false, then the code within is not executed and there is no more looping. The code following the while loop is then executed like normal.
A Real While Loop Example
Imagine that you are running an art supply store. You would like to print out the price chart for number of brushes and total cost. You sell brushes at a flat rate, but would like to display how much different quantities would cost. This will save your customers from having to do the mental math themselves.You know that a while loop would be perfect for this repetitive and boring task. Here is how to go about doing it.
Pseudo PHP Code:
$brush_price = 5;
$counter = 10;
echo "<table border=\"1\" align=\"center\">";
echo "<tr><th>Quantity</th>";
echo "<th>Price</th></tr>";
while ( $counter <= 100 ) {
echo "<tr><td>";
echo $counter;
echo "</td><td>";
echo $brush_price * $counter;
echo "</td></tr>";
$counter = $counter + 10;
}
echo "</table>";
Display:
|
Quantity
|
Price
|
|
10
|
50
|
|
20
|
100
|
|
30
|
150
|
|
40
|
200
|
|
50
|
250
|
|
60
|
300
|
|
70
|
350
|
|
80
|
400
|
|
90
|
450
|
|
100
|
500
|
- We first made a $brush_price and $counter variable and set them equal to our desired values.
- The table was set up with the beginning table tag and the table headers.
- The while loop conditional statement was checked, and $counter (10) was indeed smaller or equal to 100.
- The code inside the while loop was executed, creating a new table row for the price of 10 brushes.
- We then added 10 to $counter to bring the value to 20.
- The loop started over again at step 3, until $counter grew larger than 100.
- After the loop had completed, we ended the table.
With proper use of loops you can complete large tasks with great ease.
PHP - For Loop
The for loop is simply a while loop with a bit more code added to it. The common tasks that are covered by a for loop are:- Set a counter variable to some initial value.
- Check to see if the conditional statement is true.
- Execute the code within the loop.
- Increment a counter at the end of each iteration through the loop.
For Loop Example
Let us take the example from the while loop lesson and see how it could be done in a for loop. The basic structure of the for loop is as follows:Pseudo PHP Code:
for ( initialize a counter; conditional statement; increment a counter){
do this code;
}Notice how all the steps of the loop are taken care of in the for loop statement. Each step is separated by a semicolon: initiliaze counter, conditional statement, and the counter increment. A semicolon is needed because these are separate expressions. However, notice that a semicolon is not needed after the "increment counter" expression.
Here is the example of the brush prices done with a for loop .
PHP Code:
$brush_price = 5;
echo "<table border=\"1\" align=\"center\">";
echo "<tr><th>Quantity</th>";
echo "<th>Price</th></tr>";
for ( $counter = 10; $counter <= 100; $counter += 10) {
echo "<tr><td>";
echo $counter;
echo "</td><td>";
echo $brush_price * $counter;
echo "</td></tr>";
}
echo "</table>";
Display:
|
Quantity
|
Price
|
|
10
|
50
|
|
20
|
100
|
|
30
|
150
|
|
40
|
200
|
|
50
|
250
|
|
60
|
300
|
|
70
|
350
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80
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400
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90
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450
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100
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500
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PHP For Each Loop
Imagine that you have an associative array that you want to iterate through. PHP provides an easy way to use every element of an array with the Foreach statement.In plain english this statement will do the following:
- For each item in the specified array execute this code.
PHP For Each: Example
We have an associative array that stores the names of people in our company as the keys with the values being their age. We want to know how old everyone is at work so we use a Foreach loop to print out everyone's name and age.PHP Code:
$employeeAges;
$employeeAges["Lisa"] = "28";
$employeeAges["Jack"] = "16";
$employeeAges["Ryan"] = "35";
$employeeAges["Rachel"] = "46";
$employeeAges["Grace"] = "34";
foreach( $employeeAges as $key => $value){
echo "Name: $key, Age: $value <br />";
}
Display:
Name: Lisa, Age: 28
Name: Jack, Age: 16
Name: Ryan, Age: 35
Name: Rachel, Age: 46
Name: Grace, Age: 34
The syntax of the foreach statement is a little strange, so let's
talk about it some.Name: Jack, Age: 16
Name: Ryan, Age: 35
Name: Rachel, Age: 46
Name: Grace, Age: 34
Foreach Syntax: $something as $key => $value
This crazy statement roughly translates into: For each element of the $employeeAges associative array I want to refer to the key as $key and the value as $value.The operator "=>" represents the relationship between a key and value. You can imagine that the key points => to the value. In our example we named the key $key and the value $value. However, it might be easier to think of it as $name and $age. Below our example does this and notice how the output is identical because we only changed the variable names that refer to the keys and values.
PHP Code:
$employeeAges;
$employeeAges["Lisa"] = "28";
$employeeAges["Jack"] = "16";
$employeeAges["Ryan"] = "35";
$employeeAges["Rachel"] = "46";
$employeeAges["Grace"] = "34";
foreach( $employeeAges as $name => $age){
echo "Name: $name, Age: $age <br />";
}
Display:
Name: Lisa, Age: 28
Name: Jack, Age: 16
Name: Ryan, Age: 35
Name: Rachel, Age: 46
Name: Grace, Age: 34
Name: Jack, Age: 16
Name: Ryan, Age: 35
Name: Rachel, Age: 46
Name: Grace, Age: 34
PHP - Do While Loop
A "do while" loop is a slightly modified version of the while loop. If you recal from one of the previous lessons on While Loops the conditional statement is checked comes back true then the code within the while loop is executed. If the conditional statement is false then the code within the loop is not executed.On the other hand, a do-while loop always executes its block of code at least once. This is because the conditional statement is not checked until after the contained code has been executed.
PHP - While Loop and Do While Loop Contrast
A simple example that illustrates the difference between these two loop types is a conditional statement that is always false. First the while loop:PHP Code:
$cookies = 0;
while($cookies > 1){
echo "Mmmmm...I love cookies! *munch munch munch*";
}
Display:
PHP Code:
$cookies = 0;
do {
echo "Mmmmm...I love cookies! *munch munch munch*";
} while ($cookies > 1);
Display:
Mmmmm...I love cookies! *munch munch munch*
The code segment "Mmmm...I love cookies!" was executed even though
the conditional statement was false. This is because a do-while loop first do's
and secondly checks the while condition!Chances are you will not need to use a do while loop in most of your PHP programming, but it is good to know it's there!
PHP - POST & GET
Recall from the PHP Forms Lesson where we used an HTML form and sent it to a PHP web page for processing. In that lesson we opted to use the the post method for submitting, but we could have also chosen the get method. This lesson will review both transferring methods.POST - Review
In our PHP Forms Lesson we used the post method. This is what the pertinent line of HTML code looked like:HTML Code Excerpt:
<form action="process.php" method="post">
<select name="item">
...
<input name="quantity" type="text" />This HTML code specifies that the form data will be submitted to the "process.php" web page using the POST method. The way that PHP does this is to store all the "posted" values into an associative array called "$_POST". Be sure to take notice the names of the form data names, as they represent the keys in the "$_POST" associative array.
Now that you know about associative arrays, the PHP code from "process.php" should make a litte more sense.
PHP Code Excerpt:
$quantity = $_POST['quantity'];
$item = $_POST['item'];The form names are used as the keys in the associative array, so be sure that you never have two input items in your HTML form that have the same name. If you do, then you might see some problems arise.
PHP - GET
As we mentioned before, the alternative to the post method is get. If we were to change our HTML form to the get method, it would look like this:HTML Code Excerpt:
<form action="process.php" method="get">
<select name="item">
...
<input name="quantity" type="text" />The get method is different in that it passes the variables along to the "process.php" web page by appending them onto the end of the URL. The URL, after clicking submit, would have this added on to the end of it:
"?item=##&quantity=##"
The question mark "?" tells the browser that the following items are variables. Now that we changed the method of sending information on "order.html", we must change the "process.php" code to use the "$_GET" associative array.
PHP Code Excerpt:
$quantity = $_GET['quantity'];
$item = $_GET['item'];After changing the array name the script will function properly. Using the get method displays the variable information to your visitor, so be sure you are not sending password information or other sensitive items with the get method. You would not want your visitors seeing something they are not supposed to!
Security Precautions
Whenever you are taking user input and using you need to be sure that the input is safe. If you are going to insert the data into a MySQL database, then you should be sure you have thought about preventing MySQL Injection. If you are going to make a user's input available to the public, then you should think about PHP htmlentities.PHP - Magic Quotes
Prior to PHP 6 there was a feature called magic quotes that was created to help protect newbie programmers from writing bad form processing code. Magic quotes would automatically escape risky form data that might be used for SQL Injection with a backslash \. The characters escaped by PHP include: quote ', double quote ", backslash \ and NULL characters.However, this newbie protection proved to cause more problems than it solved and is not in PHP 6. If your PHP version is any version before 6 then you should use this lesson to learn more about how magic quotes can affect you.
Magic Quotes - Are They Enabled?
First things first, you need to check to see if you have magic quotes enabled on you server. The get_magic_quotes_gpc function will return a 0 (off) or a 1 (on). These boolean values will fit nicely into an if statement where 1 is true and 0 is false.PHP Code:
if(get_magic_quotes_gpc())
echo "Magic quotes are enabled";
else
echo "Magic quotes are disabled";
Display:
Magic quotes are enabled
If you received the message "Magic quotes are enabled" then you
should definitely continue reading this lesson, if not feel free to learn about
it in case you are developing for servers that might have quotes on or off.Magic Quotes in Action
Now lets make a simple form processor to show how machines with magic quotes enabled will escape those potentially risky characters. This form submits to itself, so you only need to make one file, "magic-quotes.php" to test it out.magic-quotes.php Code:
<?php
echo "Altered Text: ".$_POST['question'];
?>
<form method='post'>
Question: <input type='text' name='question'/><br />
<input type='submit'>
</form>This simple form will display to you what magic quotes is doing. If you were to enter and submit the string: Sandy said, "It's a beautiful day outside and I like to use \'s." You would receive the following output.
Display:
Altered Text: Sandy said,
\"It\'s a beautiful day outside and I like to use \\\'s.\"
Question:
Magic quotes did a number on that string, didn't it? Notice that there is a
backslash before all of those risky characters we talked about earlier. After
magic quotes:- A backslash \ becomes \\
- A quote ' becomes \'
- A double-quote " becomes \"
Removing Backslashes - stripslashes()
Before you use PHP's backslash removal function stripslashes it's smart to add some magic quote checking like our "Are They Enabled?" section above. This way you won't accidentally be removing slashes that are legitimate in the future if your PHP's magic quotes setting changes in the future.magic-quotes.php Code:
<?php
echo "Removed Slashes: ";
// Remove those slashes
if(get_magic_quotes_gpc())
echo stripslashes($_POST['question']);
else
echo $_POST['question'];
?>
<form method='post'>
Question: <input type='text' name='question'/><br />
<input type='submit'>
</form>Our new output for our string containing risky characters would now be:
Display:
Removed Slashes: Sandy said, "It's a beautiful day
outside and I like to use \'s."
