PHP is a powerful tool for making dynamic and interactive Web pages.

What You Should Already Know Before you continue you should have a basic understanding of the following:

• HTML/XHTML
• JavaScrit

PHP is the widely-used, free, and efficient alternative to competitors such as Microsoft’s ASP.

PHP is a widely-used general-purpose scripting language that is especially suited for Web development and can be embedded into HTML.

PHP (recursive acronym for PHP: Hypertext Preprocessor) is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML.

PHP is a server-side scripting language.

PHP stands for PHP: Hypertext Preprocessor

• PHP is a server-side scripting language, like ASP
• PHP scripts are executed on the server
• PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc.)
• PHP is an open source software
• PHP is free to download and use

What is a PHP File?

• PHP files can contain text, HTML tags and scripts
• PHP files are returned to the browser as plain HTML
• PHP files have a file extension of “.php”, “.php3″, or “.phtml”

What is MySQL?

• MySQL is a database server
• MySQL is ideal for both small and large applications
• MySQL supports standard SQL
• MySQL compiles on a number of platforms
• MySQL is free to download and use

PHP + MySQL

• PHP combined with MySQL are cross-platform (you can develop in Windows and serve on a Unix platform)

Why PHP?

• PHP runs on different platforms (Windows, Linux, Unix, etc.)
• PHP is compatible with almost all servers used today (Apache, IIS, etc.)
• PHP is FREE to download from the official PHP resource: www.php.net
• PHP is easy to learn and runs efficiently on the server side

Where to Start?

To get access to a web server with PHP support, you can:

• Install Apache (or IIS) on your own server, install PHP, and MySQL
• Or find a web hosting plan with PHP and MySQL support

What do you Need?

If your server supports PHP you don’t need to do anything. Just create some .php files in your web directory, and the server will parse them for you. Because it is free, most web hosts offer PHP support.

However, if your server does not support PHP, you must install PHP.

Here is a link to a good tutorial from PHP.net on how to install PHP5: http://www.php.net/manual/en/install.php

Download PHP

Download PHP for free here: http://www.php.net/downloads.php

Download MySQL Database

Download MySQL for free here: http://www.mysql.com/downloads/

Download Apache Server

Download Apache for free here: http://httpd.apache.org/download.cgi

The PHP script is executed on the server, and the plain HTML result is sent back to the browser.

Basic PHP Syntax

A PHP script always starts with <!–?php and ends with ?>. A PHP script can be placed anywhere in the document. On servers with shorthand-support, you can start a PHP script with . For maximum compatibility, we recommend that you use the standard form (<!–?php) rather than the shorthand form.

A PHP file must have a .php extension.

A PHP file normally contains HTML tags, and some PHP scripting code. Below, we have an example of a simple PHP script that sends the text “Hello World” back to the browser:

Each code line in PHP must end with a semicolon. The semicolon is a separator and is used to distinguish one set of instructions from another.

There are two basic statements to output text with PHP: echo and print.

In the example above we have used the echo statement to output the text “Hello World”.

Comments in PHP

In PHP, we use // to make a one-line comment or /* and */ to make a comment block:

Variables are “containers” for storing information.

Do You Remember Algebra From School?

Do you remember algebra from school? x=5, y=6, z=x+y

Do you remember that a letter (like x) could be used to hold a value (like 5), and that you could use the information above to calculate the value of z to be 11?

These letters are called variables, and variables can be used to hold values (x=5) or expressions (z=x+y).

PHP Variables

As with algebra, PHP variables are used to hold values or expressions.

A variable can have a short name, like x, or a more descriptive name, like carName.

Rules for PHP variable names:

• Variables in PHP starts with a $ sign, followed by the name of the variable
• The variable name must begin with a letter or the underscore character
• A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
• A variable name should not contain spaces
• Variable names are case sensitive (y and Y are two different variables

Creating (Declaring) PHP Variables

PHP has no command for declaring a variable. A variable is created the moment you first assign a value to it:

$myCar=”Volvo”;

After the execution of the statement above, the variable myCar will hold the value Volvo.

Tip: If you want to create a variable without assigning it a value, then you assign it the value of null.

Let’s create a variable containing a string, and a variable containing a number:

Note: When you assign a text value to a variable, put quotes around the value.

PHP is a Loosely Typed Language

In PHP, a variable does not need to be declared before adding a value to it. In the example above, notice that we did not have to tell PHP which data type the variable is. PHP automatically converts the variable to the correct data type, depending on its value. In a strongly typed programming language, you have to declare (define) the type and name of the variable before using it.

PHP Variable Scope

The scope of a variable is the portion of the script in which the variable can be referenced.

PHP has four different variable scopes:

• local
• global
• static
• parameter

Local Scope

A variable declared within a PHP function becomes local and can only be accessed within that function. (the variable has local scope).

You can have local variables with the same name in different functions, because local variables are only recognized by the function in which they are declared. Local variables are deleted as soon as the function is completed.

Global Scope

Global scope refers to any variable that is defined outside of any function. Global variables can be accessed from any part of the program that is not inside a function. To access a global variable from within a function, use the global keyword:

PHP also stores all global variables in an array called $GLOBALS[ ]. Its index is the name of the variable. This array is also accessible from within functions and can be used to update global variables directly:

global $a; $a=”abc”; // is the same as $GLOBALS[“a”]=”abc”;

Static Scope

When a function is completed, all of its variables are normally deleted. However, sometimes you want a local variable to not be deleted.

To do this, use the static keyword when you first declare the variable:

static $rememberMe;

Then, each time the function is called, that variable will still have the information it contained from the last time the function was called.

Note: The variable is still local to the function.

Parameters

A parameter is a local variable whose value is passed to the function by the calling code. Parameters are declared in a parameter list as part of the function declaration:

function myTest($para1,$para2,…) { // function code }

Parameters are also called arguments. We will discuss them in more detail when we talk about functions.

A string variable is used to store and manipulate text.

String Variables in PHP

String variables are used for values that contain characters. In this chapter we are going to look at the most common functions and operators used to manipulate strings in PHP. After we create a string we can manipulate it. A string can be used directly in a function or it can be stored in a variable.

Below, the PHP script assigns the text “Hello World” to a string variable called $txt:

The output of the code above will be:

Hello World

Now, lets try to use some different functions and operators to manipulate the string.

The Concatenation Operator

There is only one string operator in PHP.

The concatenation operator (.) is used to put two string values together. To concatenate two string variables together, use the concatenation operator:

The output of the code above will be:

Hello World! What a nice day!

If we look at the code above you see that we used the concatenation operator two times. This is because we had to insert a third string (a space character), to separate the two strings.

The strlen() function

The strlen() function is used to return the length of a string. Let’s find the length of a string:

The output of the code above will be:

12

The length of a string is often used in loops or other functions, when it is important to know when the string ends. (i.e. in a loop, we would want to stop the loop after the last character in the string).

The strpos() function

The strpos() function is used to search for a character/text within a string.

If a match is found, this function will return the character position of the first match. If no match is found, it will return FALSE.

Let’s see if we can find the string “world” in our string:

The output of the code above will be:

6

The position of the string “world” in the example above is 6. The reason that it is 6 (and not 7), is that the first character position in the string is 0, and not 1.

Complete PHP String Reference

For a complete reference of all string functions, go to our complete PHP String Reference. The reference contains a brief description, and examples of use, for each function!

The assignment operator = is used to assign values to variables in PHP. The arithmetic operator + is used to add values together.

Arithmetic Operators

The table below lists the arithmetic operators in PHP:

Assignment Operators

The basic assignment operator in PHP is “=”. It means that the left operand gets set to the value of the expression on the right. That is, the value of “$x = 5″ is 5.

Incrementing/Decrementing Operators

Comparison Operators

Comparison operators allow you to compare two values:

Logical Operators

Array Operators

Conditional statements are used to perform different actions based on different conditions.

Conditional Statements

Very often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this. In PHP we have the following conditional statements:

• if statement – use this statement to execute some code only if a specified condition is true
• if…else statement – use this statement to execute some code if a condition is true and another code if the condition is false
• if…elseif….else statement – use this statement to select one of several blocks of code to be executed
• switch statement – use this statement to select one of many blocks of code to be executed

The if Statement

Use the if statement to execute some code only if a specified condition is true.

SYNTAX

if (condition) code to be executed if condition is true;

The following example will output “Have a nice weekend!” if the current day is Friday:

Notice that there is no ..else.. in this syntax. The code is executed only if the specified condition is true.

The if…else Statement

Use the if….else statement to execute some code if a condition is true and another code if a condition is false.

SYNTAX

if (condition) code to be executed if condition is true; else code to be executed if condition is false;

EXAMPLE

The following example will output “Have a nice weekend!” if the current day is Friday, otherwise it will output “Have a nice day!”:

If more than one line should be executed if a condition is true/false, the lines should be enclosed within curly braces:

<!–?php $d=date(“D”); if ($d==”Fri”) { echo “Hello!
”; echo “Have a nice weekend!”; echo “See you on Monday!”; } ?>

The if…elseif….else Statement

Use the if….elseif…else statement to select one of several blocks of code to be executed.

SYNTAX

if (condition) code to be executed if condition is true; elseif (condition) code to be executed if condition is true; else code to be executed if condition is false;

EXAMPLE

The following example will output “Have a nice weekend!” if the current day is Friday, and “Have a nice Sunday!” if the current day is Sunday. Otherwise it will output “Have a nice day!”:

Conditional statements are used to perform different actions based on different conditions.

The PHP Switch Statement

Use the switch statement to select one of many blocks of code to be executed.

SYNTAX

switch (n) { case label1: code to be executed if n=label1; break; case label2: code to be executed if n=label2; break; default: code to be executed if n is different from both label1 and label2; }

This is how it works: First we have a single expression n (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed. Use break to prevent the code from running into the next case automatically. The default statement is used if no match is found.

EXAMPLE

An array stores multiple values in one single variable.

What is an Array?

A variable is a storage area holding a number or text. The problem is, a variable will hold only one value.

An array is a special variable, which can store multiple values in one single variable.

If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:

$cars1=”Saab”; $cars2=”Volvo”; $cars3=”BMW”;

However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?

The best solution here is to use an array!

An array can hold all your variable values under a single name. And you can access the values by referring to the array name.

Each element in the array has its own index so that it can be easily accessed.

In PHP, there are three kind of arrays:

• Numeric array – An array with a numeric index
• Associative array – An array where each ID key is associated with a value
• Multidimensional array – An array containing one or more arrays

Numeric Arrays

A numeric array stores each array element with a numeric index. There are two methods to create a numeric array.

1. In the following example the index are automatically assigned (the index starts at 0):

$cars=array(“Saab”,”Volvo”,”BMW”,”Toyota”);

2. In the following example we assign the index manually:

$cars[0]=”Saab”; $cars[1]=”Volvo”; $cars[2]=”BMW”; $cars[3]=”Toyota”;

EXAMPLE

In the following example you access the variable values by referring to the array name and index:

The code above will output:

Saab and Volvo are Swedish cars.

Associative Arrays

An associative array, each ID key is associated with a value. When storing data about specific named values, a numerical array is not always the best way to do it. With associative arrays we can use the values as keys and assign values to them.

EXAMPLE 1

In this example we use an array to assign ages to the different persons:

$ages = array(“Peter”=>32, “Quagmire”=>30, “Joe”=>34);

EXAMPLE 2

This example is the same as example 1, but shows a different way of creating the array:

$ages[‘Peter’] = “32″; $ages[‘Quagmire’] = “30″; $ages[‘Joe’] = “34″;

The ID keys can be used in a script:

<!–?php $ages[‘Peter’] = “32″; $ages[‘Quagmire’] = “30″; $ages[‘Joe’] = “34″;

echo “Peter is ” . $ages[‘Peter’] . ” years old.”; ?>

The code above will output:

Peter is 32 years old.

Multidimensional Arrays

In a multidimensional array, each element in the main array can also be an array. And each element in the sub-array can be an array, and so on.

EXAMPLE

In this example we create a multidimensional array, with automatically assigned ID keys:

$families = array ( “Griffin”=>array ( “Peter”, “Lois”, “Megan” ), “Quagmire”=>array ( “Glenn” ), “Brown”=>array ( “Cleveland”, “Loretta”, “Junior” ) );

The array above would look like this if written to the output:

Array ( [Griffin] => Array ( [0] => Peter [1] => Lois [2] => Megan ) [Quagmire] => Array ( [0] => Glenn ) [Brown] => Array ( [0] => Cleveland [1] => Loretta [2] => Junior ) )

EXAMPLE 2

Lets try displaying a single value from the array above:

echo “Is ” . $families[‘Griffin’][2] . ” a part of the Griffin family?”;

The code above will output:

Is Megan a part of the Griffin family?

Complete PHP Array Reference

For a complete reference of all array functions, go to our complete PHP Array Reference.

The reference contains a brief description, and examples of use, for each function!

Loops execute a block of code a specified number of times, or while a specified condition is true.

PHP Loops

Often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost equal lines in a script we can use loops to perform a task like this.

In PHP, we have the following looping statements:

• while – loops through a block of code while a specified condition is true
• do…while – loops through a block of code once, and then repeats the loop as long as a specified condition is true
• for – loops through a block of code a specified number of times
• foreach – loops through a block of code for each element in an array

The while Loop

The while loop executes a block of code while a condition is true.

SYNTAX

while (condition) { code to be executed; }

EXAMPLE

The example below defines a loop that starts with i=1. The loop will continue to run as long as i is less than, or equal to 5. i will increase by 1 each time the loop runs:

<!–?php $i=1; while($i<=5) { echo “The number is ” . $i . “
”; $i++; } ?>