can't access global variables inside a usort function?

Question

I\'m trying to do a usort in PHP, but I can\'t access global variables inside a usort function.

I\'ve simplified my code down to bare bones to show what I mean:

Answer 1

Can't reproduce the "error" and neither can codepad: http://codepad.org/5kwctnDP

You could also use object properties instead of global variables

<?php
class Foo {
    protected $test = 1;
    public function bar($a, $b) {
        echo 'hi' . $this->test;
        return strcmp($a, $b);
    }
}


$topics = array(1,2,3);
$foo = new Foo;
usort($topics, array($foo, 'bar'));

Answer 2

The code I put in my question was dropped inside a template on bbPress, which is the forum cousin to Wordpress. A friend told me that "Sometimes PHP will act weird if you don't global a variable before you define it, depending on how nested the code is when it's executed - bbPress does some complex includes by the time the template outputs".

So I tried that and it works:

global $hi123;
$hi123 = ' working ';

I'm answering my own question in case another idiot like me finds this in a Google search. :-)

I'm going to accept VolkerK's answer, though, because the object workaround is pretty clever.

Answer 3

It is working as of php 5.2.4

$testglobal = ' WORKING ';
$topics = array('a','b','c');      
function cmp($a, $b) {
    global $testglobal;
    echo 'hi' . $testglobal;
}
usort($topics, "cmp");
// hi WORKING hi WORKING 

Answer 4

Does it work if you access the variable using the super-global $GLOBALS array?

$testglobal = 1;
function cmp($a, $b) {
    echo 'hi' . $GLOBALS['testglobal'];
}
usort($topics, "cmp");