$b)?1:-1; } function myfunction_value($a,$b) { if ($a===$b) { return 0; } return ($a>$b)?1:-1; } $a1 = array("a"=>"red","b"=>"green","c"=>"blue"); $a2 = array("a"=>"red","b"=>"green","c"=>"green"); $result = array_udiff_uassoc($a1,$a2,"myfunction_key","myfunction_value"); print_r($result);