gistfile1.php

<?php
$host_meta = fetch_host_meta($curl, $parsed['scheme'], $parsed['domain'], $identifier);

if (isset($host_meta['lrdd']['priority'])) {
  $priority = $host_meta['lrdd']['priority'];
} else {
  $priority = 'host';
}

$link_href = false;
if (!$host_meta || $priority == 'resource' || !isset($host_meta['openid']['token_endpoint'])) {
  $links = fetch_identifier($curl, $identifier);

  if ($links['header'] && $links['html']) {
    $link_href = $priority == 'host' ? $links['header'] : $links['html'];
  } else if ($links['header']) {
    $link_href = $links['header'];
  } else if ($links['html']){
    $link_href = $links['html'];
  }
}


// given an identifier either returns an associative array with keys
// of header and html or false on failure.
function fetch_identifier($curl, $identifier) {
  // can't fetch emails
  if (strpos($identifier, 'acct:') === 0) {
    return false;
  }

  curl_setopt($curl, CURLOPT_URL, $identifier);
  curl_setopt($curl, CURLOPT_HEADER, true);
  list($header, $html) = explode("\r\n\r\n", curl_exec($curl), 2);
  curl_setopt($curl, CURLOPT_HEADER, false);

  if (!$html) {
    return false;
  }

  $header_href = '';
  $html_href = '';

  // this now needs to parse the dom and look for a link tag in the head
  // with a rel of openid.
  $old_libxml_error = libxml_use_internal_errors(true);
  $doc = new DOMDocument();
  $doc->loadHTML($html);
  libxml_use_internal_errors($old_libxml_error);

  $head = $doc->getElementsByTagName('head');
  if ($head->length > 0) {
    foreach ($head->item(0)->getElementsByTagName('link') AS $link) {
    	if ($link->hasAttribute('rel')) {
    		$rel = $link->getAttribute('rel');
    		$rel_values = explode(' ', $rel);
    		foreach ($rel_values AS $value) {
    			if ($value == 'openid') {
    				$html_href = $link->getAttribute('href');
    				break 2;
          }
        }
      }
    }
  }

  $headers = explode("\r\n", $header);
  foreach ($headers AS $header) {
    if (stripos($header, 'Link:') === 0) {
      list(,$link_value) = explode(': ', $header, 2);
      $link_params = explode(';', $link_value);
      $link_uri = array_shift($link_params);

      if ($link_uri[0] !== '<' || substr($link_uri, -1) !== '>') {
        break;
      }
    
      // trim < and > from the end
      $link_uri = substr($link_uri, 1, -1);

      foreach ($link_params AS $link_param) {
        $link_param = trim($link_param);
        if (strpos($link_param, 'rel=') === 0) {
          preg_match('/"((?:[^"]).*)"/', $link_param, $matches);
          if (isset($matches[1])) {
            $rel_values = explode(' ', $matches[1]);
            foreach ($rel_values AS $value) {
        			if ($value == 'openid') {
        			  $header_href = $link_uri;
        				break 3;
              }
            }
          }
        }
      }
    }
  }

  return array(
    'header' => $header_href,
    'html'   => $html_href
  );
}