code: private static function filterArray($needle, $heystack, $always = array())
      {
          foreach($heystack as $k => $v)
          {
              if( !in_array($v, $needle) && !in_array($v, $always) )
                  unset($heystack[$k]);
          }
          
          return $heystack;
      }
docs: System Helpers below