<?php

// http://pl.wikipedia.org/wiki/Dzielnik#Cechy_podzielno.C5.9Bci

function Division11Simple($iInteger)
{
  return (bool)($iInteger%11 == 0);
}

function Division11Advenced($iInteger)
{
  $aNumbers = str_split((string)$iInteger);
  $iEven = 0;
  $iOdds = 0;
  
  foreach($aNumbers as $iPlace => $iNumber)
  {
    $iNumber = (int)$iNumber;
    
    if($iPlace%2 == 0)
      $iEven += $iNumber;
    else
      $iOdds += $iNumber;
  }
  
  return (bool)(($iEven - $iOdds)%11 == 0);
}

var_dump( Division11Simple(121) );
var_dump( Division11Advenced(121) );

?>