code: protected function isEmpty($value)
      {
          return $value === '' || $value === [] || $value === null || is_string($value) && trim($value) === '';
      }
docs: Returns a value indicating whether the give value is "empty".
  
  The value is considered "empty", if one of the following conditions is satisfied:
  
  - it is `null`,
  - an empty string (`''`),
  - a string containing only whitespace characters,
  - or an empty array.
  
  @param mixed $value
  @return bool if the value is empty