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

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");