$array1 = array(1,3,5,7,8,9);
$array2 = array(2,3,9);
in_array и array_search
?$array1 = array(1, 3, 5, 7, 8, 9);
$array2 = array(2, 3, 9);
$intersect = array_intersect($array1, $array2);
var_dump($intersect); // => array(3, 9)
$result = !empty($intersect);
var_dump($result); // => true