Luhn's Algorithm PHP

lunhAlgorithm.php

<?php
/**
* @see http://en.wikipedia.org/wiki/Luhn_algorithm
*/
function is_valid_luhn($number) {
  $number = preg_replace("/[^0-9]/", "", $number);
  settype($number, 'string');
  $sumTable = array(
    array(0,1,2,3,4,5,6,7,8,9),
    array(0,2,4,6,8,1,3,5,7,9)
  );
  $sum = 0;
  $flip = 0;
  for ($i = strlen($number) - 1; $i >= 0; $i--) {
    $sum += $sumTable[$flip++ & 1][$number[$i]];
  }
  return $sum % 10 === 0;
}