code: private static function filterConstantsByLevel($constants, $level)
      {
          foreach ($constants as $constantName => $value) {
              if (!self::inBitmask($value, $level)) {
                  unset($constants[$constantName]);
              }
          }
          unset($constants['E_ALL']);
          return $constants;
      }
docs: Get all constants included in specified error level
  excludes E_ALL
  
  @param array   $constants constantName => value array
  @param integer $level     error level
  
  @return array