PHP -  Variable Scope

The scope of a variable is the context within which a variable is available. There are two scopes for variables in PHP. Global variables are available directly from the mainline PHP execution. That is, if you are not inside a function, you can access global variables directly. Unlike most other languages, functions in PHP have their own, completely separate variable scope. Take this example:

<?php

function test( ) {

echo $a;

}



$a = "Hello World";

test( ); 

?>

If you run this script you will find that there is no output. This is because the $a you are trying to access inside the test( ) function is a completely different variable from the global $a you created in the global scope just before calling the function. In order to access a globally-scoped variable from inside a function, you need to tell the function to use the global scope for that particular variable. It can be done with the global keyword like this:

<?php

function test( ) {

global $a;

echo $a;

}



$a = "Hello World";

test( ); 

?>

Alternatively, you can use the $GLOBALS array like this:

<?php

function test( ) {

echo $GLOBALS['a'];

}



$a = "Hello World";

test( ); 

?>

In this last example, the $GLOBALS array is known as a superglobal, which is a variable that is automatically available in all scopes without needing to be declared global in order to be accessed from within a function.

Comment an article   Name   E-mail    Title Available characters: 4000  Notify me of follow-up comments Enter what you see:

No comment posted