Check Palindrome

palindrome.php

<?php

$input = "was it a car or a cat I saw?";

$input = preg_replace("/[^a-zA-Z0-9]/", "", $input);

$string = strtolower(implode("", str_split(str_replace(' ', '', $input))));

$evenOrOdd = function($string) {
    return (strlen($string) % 2 == 0) ? "even" : "odd";
};

echo ($string == strrev($string)) ? "Is an {$evenOrOdd($string)} palindrome." : "Not a palindrome.";