Question

Recently stumbled upon this neat little bug or ‘feature’ in PHP:

function myCmpFunc($a,$b) {
    function inner($p) {
         // do something
    }
    $inner_a = inner($a);
    $inner_b = inner($b);
    if ($inner_a == $inner_b) return 0;
    return ($inner_a > $inner_b ? -1 : 1);
}

Results in a fatal error “cannot redeclare function inner in …”, when called like this

usort($myArray, 'myCmpFunc');

It works flawlessly when function inner is declared outside of myCmpFunc
and/or $myArray has not more than 2 elements 😉

— edit —

somehow Related:
PHP Fatal error: Cannot redeclare function

So here is my question, then:
Is it possible to declare functions in local scope?

— edit 2 —

Maybe, this works well in PHP 5.3 just read it has closures, yeehaa!

Answer 1

function inner($p) is defined each time that function myCmpFunc($a,$b) is executed. Furthermore, the inner function is visible outside function myCmpFunc($a,$b) after that (which pretty much takes the sense out of allowing nested function definitions). That’s why you get a duplicate definition error when you call the outer function a second time.

To work around this, check whether function_exists in the body of function myCmpFunc($a,$b).