$b ) ? 1 : -1; } $a1 = array("a"=>"red","b"=>"green","c"=>"blue"); $a2 = array("a"=>"black","b"=>"yellow","d"=>"brown"); $a3 = array("e"=>"purple","f"=>"white","a"=>"gold"); $result = array_diff_ukey($a1,$a2,$a3,"myfunction"); print_r($result);