PHP4Novice
PHP TUTORIAL
By
Engr. F. Azam, B.Sc(CSE), CCNA.
Developing Dynamic Web Applications
—————————————————-
Table of Contents
<!–[if !supportLists]–> <!–[endif]–>PHP Basics
<!–[if !supportLists]–> <!–[endif]–>Introduction
<!–[if !supportLists]–> <!–[endif]–>Installation
<!–[if !supportLists]–> <!–[endif]–>Syntax
<!–[if !supportLists]–> <!–[endif]–>Variables
<!–[if !supportLists]–> <!–[endif]–>Echo
<!–[if !supportLists]–> <!–[endif]–>Strings
<!–[if !supportLists]–> <!–[endif]–>Operators
<!–[if !supportLists]–> <!–[endif]–>Comments
<!–[if !supportLists]–> <!–[endif]–>Include File
<!–[if !supportLists]–> <!–[endif]–>Require
<!–[if !supportLists]–> <!–[endif]–>If Statement
<!–[if !supportLists]–> <!–[endif]–>If…Else
<!–[if !supportLists]–> <!–[endif]–>Elseif
<!–[if !supportLists]–> <!–[endif]–>Switch
<!–[if !supportLists]–> <!–[endif]–>Forms
<!–[if !supportLists]–> <!–[endif]–>Functions
<!–[if !supportLists]–> <!–[endif]–>Arrays
<!–[if !supportLists]–> <!–[endif]–>While Loop
<!–[if !supportLists]–> <!–[endif]–>For Loop
<!–[if !supportLists]–> <!–[endif]–>For Each
<!–[if !supportLists]–> <!–[endif]–>Do While
<!–[if !supportLists]–> <!–[endif]–>POST & GET
<!–[if !supportLists]–> <!–[endif]–>Magic Quotes
<!–[if !supportLists]–> <!–[endif]–>htmlentities
PHP Tutorial - Learn 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:
<!–[if !supportLists]–> <!–[endif]–>Customize PHP scripts that you download, so that they better fit your needs.
<!–[if !supportLists]–> <!–[endif]–>Begin to understand the working model of PHP, so you may begin to design your own PHP projects.
<!–[if !supportLists]–> <!–[endif]–>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. Inventor Rasmus Lerdorf.
PHP - What is it?
“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:
<!–[if !supportLists]–> <!–[endif]–>Reduce the time to create large websites.
<!–[if !supportLists]–> <!–[endif]–>Create a customized user experience for visitors based on information that you have gathered from them.
<!–[if !supportLists]–> <!–[endif]–>Open up thousands of possibilities for online tools. Check out PHP - HotScripts for examples of the great things that are possible with PHP.
<!–[if !supportLists]–> <!–[endif]–>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:
<!–[if !supportLists]–> <!–[endif]–>HTML - Know the syntax and especially HTML Forms.
<!–[if !supportLists]–> <!–[endif]–>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:
<!–[if !supportLists]–> <!–[endif]–>A web hosting account that supports the use of PHP web pages and grants you access to MySQL databases.
<!–[if !supportLists]–> <!–[endif]–>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 (http://www.php.net) based on the operating system that you are using.
<!–[if !supportLists]–> <!–[endif]–>PHP - Windows - Windows Installation Guide
<!–[if !supportLists]–> <!–[endif]–>PHP - Mac - Mac Installation Guide
<!–[if !supportLists]–> <!–[endif]–>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(http://www.mysql.com) Installation Guide for help on installing MySQL.
PHP Installation Troubles
If you have any installation troubles you may visit online communities for help on this common problem.
PHP Builder - A web forum for PHP users. (http://www.phpbuilders.com)
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’s syntax and semantics are similar to most other programming languages (C, Java, Perl) with the addition that all PHP code is contained with a tag, of sorts. All PHP code must be contained within the following…
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 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 function echo to write “Hello World!” and we will be talking in greater depth about this PHP function and many others 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.
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;
If you forget that dollar sign at the beginning, it will not work. This is a common mistake for new PHP programmers!
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.
<!–[if !supportLists]–>
<!–[endif]–>PHP variables must start with a letter or underscore “_”.
<!–[if !supportLists]–> <!–[endif]–>PHP variables may only be comprised of alpha-numeric characters and underscores. a-z, A-Z, 0-9, or _ .
<!–[if !supportLists]–> <!–[endif]–>Variables with more than one word should be separated with underscores. $my_variable
<!–[if !supportLists]–> <!–[endif]–>Variables with more than one word can also be distinguished with capitalization. $myVariable.
PHP - Echo
As you saw in the previous lesson, the PHP function echo is a means of outputting text to the web browser. Throughout your PHP career you will be using the echo function 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 the PHP echo function. 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! The echo function 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:
<!–[if !supportLists]–> <!–[endif]–>Don’t use quotes inside your string
<!–[if !supportLists]–> <!–[endif]–>Escape your quotes that are within the string with a slash. To escape a quote just place a slash directly before the quotation mark, i.e. \”
<!–[if !supportLists]–> <!–[endif]–>Use single quotes (apostrophes) for quotes inside your string.
See our example below for the right and wrong use of the echo function:
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 slash in front of it ( \” ). The slash 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 combine text strings and variables. By doing such a conjunction you save yourself from having to do a large number of echo statements. Variables and text strings are joined together with a period ( . ). The example below shows how to do such a combination.
PHP Code:
<?php
$my_string = “Hello Bob. My name is: “;
$newline = “<br />”;
echo $my_string.”Bobettta”.$newline;
echo “Hi, I’m Bob. Who are you? “.$my_string.$newline;
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
This combination can be done multiple times, as the example shows. This method of joining two or more strings together is called concatenation and we will talk more about this and other forms of string manipulation in our string lesson.
PHP - Strings
In the last lesson, PHP Echo, 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 place the string directly into a function.
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 function 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 - 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.
<!–[if !supportLists]–> <!–[endif]–>Assignment Operators
<!–[if !supportLists]–> <!–[endif]–>Arithmetic Operators
<!–[if !supportLists]–> <!–[endif]–>Comparison Operators
<!–[if !supportLists]–> <!–[endif]–>String Operators
<!–[if !supportLists]–> <!–[endif]–>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
Now both $my_var and $another_var contain the value 4. Assignments can also be used in conjunction with arithmetic operators.
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.
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 If Statement 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 Echo Lesson, 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;
However, there is a shorthand for doing this.
$counter += 1;
This combination assignment/arithmetic operator would accomplish the same task. The downside to this combination operator is that it reduces code readability to those programmers who are not used to such an operator. Here are some examples of other common shorthand operators. In general, “+=” and “-=” are the most widely used combination operators.
|
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;
To subtract 1 from a variable, or “decrement” use the “–” operator:
$x–; Which is equivalent to $x -= 1; or $x = $x - 1;
In addition to this “shorterhand” technique, you can specify whether you want the increment to before the line of code is being executed or after the line has executed. Our PHP code below will display the difference.
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.
PHP - Comments
Comments in PHP are similar to comments that are used in HTML. The PHP comment syntax always begins with a special character sequence and all text that appears between the start of the comment and the end will be ignored by the browser.
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 “//” 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!”;
?>
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.
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.
IF STATEMENT
PHP – If Statement
The PHP if statement is very similar to other programming languages use of 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, occurring 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!
“;
}
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.
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!
“;
}
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!
PHP – If … Else Conditional Statement
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 !supportLists]–> <!–[endif]–>If you work hard then you will succeed.
<!–[if !supportLists]–> <!–[endif]–>Else, if you do not work hard, then you will fail.
How does this translate into something useful for PHP developers? Well consider this:
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.
<!–[if !supportLists]–> <!–[endif]–>We first made a PHP variable called $number_three and set it equal to 3.
<!–[if !supportLists]–> <!–[endif]–>In this example we compared a variable to an integer value. To do such a comparison we use “==”, which in English means “Is Equal To”.
<!–[if !supportLists]–> <!–[endif]–>$number_three is indeed Equal To 3 and so this statement will evaluate to true.
<!–[if !supportLists]–> <!–[endif]–>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.
<!–[if !supportLists]–> <!–[endif]–>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 if statement was false. As you can see, the code segment contained within the else was used in this case.
PHP – ElseIf Statement
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.
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: there is no case before default.
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!
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:
<!–[if !vml]–>
<!–[endif]–>Tizag Art Supply Order Form