PHP VARIABLES

In this tutorial we are going to discuss about variable. We can distribute the variable in the following
categories:-

Basics

Predefined Variables

Variable scope

Variable variables

Basic:-

In PHP we define the variable with the ‘$’ sign. The variable name is case sensitive. A variable name
always starts with the letter and underscore.

Example

$a = 'Mike';
$a = 'John';

Predefined Variables:-

PHP provide the predefined variable. Mostly these variables are globally accessible.

Example:-

Superglobals — Superglobals are built-in variables that are always available in all scopes

$GLOBALS — References all variables available in global scope

$_SERVER — Server and execution environment information

$_GET — HTTP GET variables

$_POST — HTTP POST variables

$_FILES — HTTP File Upload variables

$_REQUEST — HTTP Request variables

$_SESSION — Session variables

$_ENV — Environment variables

$_COOKIE — HTTP Cookies

Variable scope:-

Variable scope means the context in which variable accessible. We are trying to explain the scope with
some example:-

Example:-

$a = 1;
include 'b.inc';

In the above example ‘$a’ is global or accessible for include file.

$a = 1; /* global scope */

function test()
{

$a=5;

echo $a; /* reference to local scope variable */

}

test();

echo $a;

Above
the above variable ($a = 1) scope outside the function. It’s not effective
from function variable.

If you want to use the global variable with in function then you need to use
the

$a = 1;
$b = 2;

function Sum()
{
    global $a, $b;

    $b = $a + $b;
}

Sum();
echo $b;

The above result is ‘3’.

Variable variables:-

Some time we need variable variables for dynamic uses. First we take a normal variable. After assign
the value we again assign the value but this time we use ‘$$’ with the variable.

Example:-

$a = 'hello';

$$a = 'world';

echo