array_intersect

<?

$array1 = array("a" => 0, "b" => 1, "c" => 2, "d" => 3);
$array2 = array("a" => 0, "b" => 4, "e" => 2, "f" => 5);

$return = array_intersect($array1, $array2);

print_r($return);

?>

Array
(
    [a] => 0
    [c] => 2
)

<?

$array1 = array("a" => 0, "b" => 1, "c" => 2, "d" => 3);
$array2 = array("a" => 0, "b" => 4, "e" => 2, "f" => 5);
$array3 = array("a" => 0, "b" => 4, "e" => 2, "f" => 5);

$return = array_intersect($array1, $array2, $array3);

print_r($return);

?>

Array
(
    [a] => 0
    [c] => 2
)