Anonymous functions in PHP 5.3

anonfunctions.php

<?php

$my_array = array(1, 2, 3);

$new_array = array_map(function($num) { return $num * 2; }, $my_array); // $new_array: [2, 4, 6]

// Why the arguments are in the opposite order, I have no idea ...
$new_array2 = array_filter($my_array, function($num) { return $num % 2 == 0; }); // $new_array2: [2]