/**
     * Validate PIS (Programa de Integracao Social)
     * Allows the following formats
     * XXX.XXX.XXX-XX, XXXXXXXXXXX or 
     * any combination with dots and/or hyphens 
     * @param string $pis pis code
     * @return bool
     */
    function pis($pis)
    {
      static $sum = 0;

      if (strlen($pis) === 0) {
          return false;
      }

      $pis = str_replace(array("-","."), "", $pis);
    
      if (strlen($pis) !== 11) {
          return false;
      }
 
      $multiplier = array(3,2,9,8,7,6,5,4,3,2);
      
      for($i = 0; $i < 10; $i++)    
      {   
          $sum += (int) $pis[$i] * $multiplier[$i];
      }
 
      $mod = $sum % 11;
 
      $mod = ($mod < 2)  ? 0 : 11 - $mod;  
      
      return ( (int) $pis[10] === $mod);

    }