code: protected function parseContentType($contentType)
      {
          if(false === stripos($contentType, ';')) {
              throw new ParserException('ContentType does not contain a \';\'');
          }
  
          list($mime, $boundary) = explode(';', $contentType, 2);
          list($key, $boundaryValue) = explode('=', trim($boundary), 2);
  
          if('boundary' != $key) {
              throw new ParserException('Boundary does not start with \'boundary=\'');
          }
  
          return [strtolower(trim($mime)), $boundaryValue];
      }
docs: Helper or parsing the Content-Type.
  
  @param $contentType
  @return array
  @throws ParserException