Three functions to check whether a number is a palindrome number.

isPalindrome.php

<?php
function isPalindromA($num) {
    $num = $num . '';
    $len  = strlen($num);

    for($i = 0; $i < $len / 2; $i++)
        if($num[$i] !== $num[$len - 1 - $i])
            return false;

    return true;
}

function isPalindromB($num) {
    $num = $num . '';
    $len = strlen($num);

    if($len & 1) { // odd
        $num = substr_replace($num, '', $len / 2, 1);
    }

    return substr($num, 0, strlen($num) / 2) == strrev(substr($num, strlen($num) / 2));
}

function isPalindromC($num) {
    return $num == strrev($num);
}