array_intersect_key

<?

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

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

print_r($return);

true

<?

$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);

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

print_r($return);

Array
(
    [name] => root
    [passwd] => x
    [uid] => 0
    [gid] => 0
    [gecos] => root
    [dir] => /root
    [shell] => /bin/bash
)