public function _findWebmentionEndpointInHTML($body) {
    if(preg_match('/<link[ ]+href="([^"]+)"[ ]+rel="(?:webmention ?|http:\/\/webmention\.org\/? ?)+"[ ]*\/?>/i', $body, $match)
        || preg_match('/<link[ ]+rel="(?:webmention ?|http:\/\/webmention\.org\/? ?)+"[ ]+href="([^"]+)"[ ]*\/?>/i', $body, $match)) {
      return $match[1];
    }  else {
      return false;
    }
  }


  OR


    public function _findWebmentionEndpointInHTML($body) {
    if(preg_match('/<link[ ]+href="([^"]+)"[ ]+rel=".*?webmention.*?"[ ]*\/?>/i', $body, $match)
        || preg_match('/<link[ ]+rel=".*?webmention.*?"[ ]+href="([^"]+)"[ ]*\/?>/i', $body, $match)) {
      return $match[1];
    }  else {
      return false;
    }
  }