PHP palindrome

palindrome

<?php

$strings = array("racecar", "bob", "b", "abc", "car", "mom", "diary", null, '');

foreach ($strings as $str) {
    if (palindrome($str)) {
        print "$str is a palindrome\n";
    } else {
        print "$str is NOT a palindrome\n";
    }
}

function palindrome($str)
{
    if (!is_string($str)) {
        return false;
    }

    $length = strlen($str);
    for ($i = 0; $i < (int)($length / 2); $i++) {
        if ($str[$i] != $str[$length-$i-1]) {
            return false;
        }
    }

    return true;
}

// cheat
function palindrome2($str)
{
    return ($str == strrev($str));
}