Check if a number is Palindrome, fixed GeeksForGeeks version

gistfile1.php

<?php
// A recursive PHP program to
// check whether a given number
// is palindrome or not

// A function that reurns true
// only if num contains one digit
function oneDigit($num)
{
    // comparison operation is faster
    // than division operation. So
    // using following instead of
    // "return num / 10 == 0;"
    return (($num >= 0) &&
        ($num < 10));
}

// A recursive function to find
// out whether num is palindrome
// or not. Initially, dupNum
// contains address of a copy of num.
function isPalUtil($num, &$dupNum)
{
    // Base case (needed for recursion
    // termination): This statement
    // mainly compares the first digit
    // with the last digit
    if (oneDigit($num)) {
        return ($num == ($dupNum) % 10);
    }

    // This is the key line in this
    // method. Note that all recursive
    // calls have a separate copy of
    // num, but they all share same
    // copy of *dupNum. We divide num
    // while moving up the recursion tree
    if (!isPalUtil((int)($num / 10), $dupNum)) {
        $dupNum = false;
        return false;
    }

    if ($dupNum === false) {
        return false;
    }
    // The following statements are
    // executed when we move up the
    // recursion call tree
    $dupNum = (int)($dupNum / 10);

    // At this point, if num%10
    // contains i'th digit from
    // beiginning, then (*dupNum)%10
    // contains i'th digit from end

    return ($num % 10 == ($dupNum) % 10);
}

// The main function that uses
// recursive function isPalUtil()
// to find out whether num is
// palindrome or not
function isPal($num)
{
    // If num is negative,
    // make it positive
    if ($num < 0)
        $num = (-$num);

    // Create a separate copy of
    // num, so that modifications
    // made to address dupNum
    // don't change the input number.
    $dupNum = ($num); // *dupNum = num

    return isPalUtil($num, $dupNum);
}

// Driver Code
$n = 1234321;