PHP Variables

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.

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

There are a few rules that you need to follow when choosing a name for your PHP variables.

Ø  PHP variables must start with a letter or underscore "_".

Ø  PHP variables may only be comprised of alpha-numeric charactehrs and underscores. a-z, A-Z, 0-9, or _ .

Ø  Variables with more than one word should be separated with underscores. $my_variable

Ø Variables with more than one word can also be distinguished with capitalization. $myVariable

Scope of Variables

 1.      Local Variables

2.      Global Variables

3.      Static Variables

1.      Local Variables

A variable declared within a PHP function is local and can only be accessed within that function.

2.      Global Variables

A variable that is defined outside of any function has a global scope.

Global variables can be accessed from any part of the script, EXCEPT from within a function.

3.      Static Variables

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:

Local Example	Global Example	Static Example
<?php $x=5; // global scope function myTest() { echo $x; // local scope } myTest(); ?>	<? php $x=5; // global scope $y=10; // global scope function myTest() { global $x,$y; $y=$x+$y; } myTest(); echo $y; // outputs 15 ?>	<?php function myTest() { static $x=0; echo $x; $x++; } myTest(); myTest(); myTest(); ?>