Function used by uasort to sort structured arrays by weight.
function element_sort($a, $b) {
$a_weight = is_array($a) && isset($a['#weight']) ? $a['#weight'] : 0;
$b_weight = is_array($b) && isset($b['#weight']) ? $b['#weight'] : 0;
if ($a_weight == $b_weight) {
return 0;
}
return $a_weight < $b_weight ? -1 : 1;
}