上次写了Windows Live ID当作OpenID使用的方法，这次写Google的OpenID的实现方法。

 if(empty($_REQUEST['openid_mode'])){
  $openid_server = getXrdsUri('https://www.google.com/accounts/o8/id');
  $data['openid.ns'] = 'http://specs.openid.net/auth/2.0';
  $data['openid.mode'] = 'associate';
  $data['openid.assoc_type'] = 'HMAC-SHA1';
  $data['openid.session_type'] = 'no-encryption';
  $AssocHandle = getAssociationHandle($openid_server.'?'.http_build_query($data));
  setcookie('cookieAssocHandle', $AssocHandle);
  unset($data);

  $data['openid.ns'] = 'http://specs.openid.net/auth/2.0';
  $data['openid.claimed_id'] = 'http://specs.openid.net/auth/2.0/identifier_select';
  $data['openid.identity'] = 'http://specs.openid.net/auth/2.0/identifier_select';
  $data['openid.return_to'] = $AuthUrl;
  $data['openid.realm'] = $RealmUrl;
  $data['openid.assoc_handle'] = $AssocHandle;
  $data['openid.mode'] = 'checkid_setup';
  $data['openid.ns.ext1'] = 'http://openid.net/srv/ax/1.0';
  $data['openid.ext1.mode'] = 'fetch_request';
  $data['openid.ext1.type.email'] = 'http://axschema.org/contact/email';
  $data['openid.ext1.required'] = 'email';

  $LocationUrl  = $openid_server.'?'.http_build_query($data);
 }else{
  if('id_res' == $_REQUEST['openid_mode']
   && $AssocHandle == $_REQUEST['openid_assoc_handle']){
   $openid = !empty($_REQUEST['openid_ext1_value_email']) ? $_REQUEST['openid_ext1_value_email'] : formUrl($_REQUEST['openid_claimed_id']);
   $email = $_REQUEST['openid_ext1_value_email'];
  }
  echo('<pre>');
  echo("<a href=$LoginUrl>BACK</a>\n\n");
  print_r($_REQUEST);
  echo('</pre>');
 }

function getAssociationHandle($url){
$c = curl_init($url);

curl_setopt($c, CURLOPT_RETURNTRANSFER, true);
curl_setopt($c, CURLOPT_HEADER, false);
curl_setopt($c, CURLOPT_SSL_VERIFYPEER, false);

$contents = curl_exec($c);
//print_r($contents);
//exit;

curl_close($c);

$assoc_handle = time();

$lines = explode("\n", $contents);

foreach($lines as $line){
 if(substr($line, 0, 13) == "assoc_handle:"){
  $assoc_handle = substr($line, 13);
  break;
 }
}

return $assoc_handle;
}

function getXrdsUri($url){
$c = curl_init($url);

curl_setopt($c, CURLOPT_RETURNTRANSFER, true);
curl_setopt($c, CURLOPT_HEADER, false);
curl_setopt($c, CURLOPT_SSL_VERIFYPEER, false);

$request_contents = curl_exec($c);

curl_close($c);

$domdoc = new DOMDocument();
$domdoc->loadXML($request_contents);

$uri = $domdoc->getElementsByTagName("URI");
$uri = $uri->item(0)->nodeValue;

return $uri;
}

if(empty($openid))
LocationHtml($LocationUrl);

LocationHtml函数见Windows Live ID当作OpenID使用的方法。

注意：Google的OpenID的openid.claimed_id（即OpenID）的值，随不同网站变化，网站不同值也不同，所以不是真正的OpenID，Google真正的OpenID是他的Email。但是Email也不是每次都可以取得到的，如果你在Google的授权页面上点选了”允许 XXX 记住我”，再次登录时将略过授权页面，同时也将得不到Email的值。只有Google帐号的所有者在个人设置里更改获授权网站，将你的网站撤销访问权，才能再次得到Email的值。

Google的OpenID是个被阉割的OpenID，除了提供Email的值之外，其他一概不提供！

参考：http://code.google.com/intl/zh-CN/apis/accounts/docs/OpenID.html