- var_dump: documentation ( source)
- array_diff: documentation ( source)
<?php
$one = array('a' => array(1,2,3), array(8,6,7));
$second = array('b' => array(), array(2,3,4), array(7,4,5), array(1,4,5));
$res = array_diff($one, $second);
var_dump($res);