- var_dump: documentation ( source)
- array_search: documentation ( source)
<?php
$x = function(){};
$y = function($x){echo 'foo';};
$z = function($x){echo 'bar';};
var_dump(array_search($x, array($x,$y,$z), false));
var_dump(array_search($y, array($x,$y,$z), false));
var_dump(array_search($z, array($x,$y,$z), false));
var_dump(array_search(function(){}, array($x,$y,$z), false));