<?php

$nums = range(0, 9);
$char = "w";

var_dump(in_array($char, $nums)); // "w" == 0 ?? yep.

//

$nums = range('0', '9'); // => [0, 1, 2, ...] why??
$char = '2';

var_dump(in_array($char, $nums, true)); // strict compare