PHP global variables not working inside a function [duplicate]

Question

Possible Duplicate:
php function variable scope

I am using below code to test with a global variable. It seems that a global variable cannot be compared inside a function.

Why is it not displaying 'hello world' in the output?

Below is the code that I am trying:

<?php    
$bool = 1;

function boo() {
    if ($bool == 1) {
        $bool = 2;
        echo 'Hello World';    
    }
}
?> 

When I remove function boo(), 'hello world' is displayed. Why is it not displaying when function exists?

Answer 1

use global $var to access your variable

<?php    
$bool = 1;

function boo() {
    global $bool;
    if ($bool == 1) {
        $bool = 2;
        echo 'Hello World';    
    }
}

boo();
?>

Or a safer way using pointers would be to

function boo(&$bool) {
    if ($bool == 1) {
        $bool = 2;
        echo 'Hello World';
    }
}