gistfile1.php

<?php

  /**
   * Validates the response.
   *
   * @return sfTestFunctionalBase|sfTester
   */
  public function isValid()
  {
    if (preg_match('/(x|ht)ml/i', $this->response->getContentType(), $matches))
    {
      $revert = libxml_use_internal_errors(true);

      $dom = new DOMDocument('1.0', $this->response->getCharset());
      if ($dom->loadXML($this->response->getContent()))
      {
        $this->tester->pass(sprintf('response validates as "%s"', $dom->doctype->name ? $dom->doctype->name : 'xml'));
      }
      else
      {
        $this->tester->fail(sprintf('response validates as "%s"', $dom->doctype->name ? $dom->doctype->name : 'xml'));
        foreach (libxml_get_errors() as $error)
        {
          $this->tester->diag('    '.trim($error->message));
        }
      }

      libxml_use_internal_errors($revert);
    }
    else
    {
      throw new LogicException(sprintf('Unable to validate responses of content type "%s"', $this->response->getContentType()));
    }

    return $this->getObjectToReturn();
  }