Update InArray.php

if haystack is an empty array, an exception 'haystack option is mandatory' is thrown
should be exact equality ===

<?php
$t = array();
if ($t == null) echo "null\n"; else echo "not null\n";

this code echoes null

<?php
$t = array();
if ($t === null) echo "null\n"; else echo "not null\n";

this code echoes not null