How to Get Channel id or url after Google Oauth PHP

i am trying to code an application system with youtube login. but i have an issue After i get required authorisation with oauth 2.0 i want to get choosen youtube channel id in a string but i could not do it can somebody please help me.

    $client = new Google_Client();    $client->setClientId($client_id);    $client->setClientSecret($client_secret);    $client->setRedirectUri($redirect_uri);    $client->setApplicationName("BYTNETWORK");    $client->setScopes(array('https://www.googleapis.com/auth/userinfo.profile','https://www.googleapis.com/auth/yt-analytics.readonly'      ));if (isset($_SESSION['access_token']) && $_SESSION['access_token']) {  $client->setAccessToken($_SESSION['access_token']);} else {  $authUrl = $client->createAuthUrl();}

so after this i want a string like

$channelid = "xxxxx"; to use it in code below

$data = file_get_contents('http://gdata.youtube.com/feeds/api/users/$channelid?alt=json');$data = json_decode($data, true);$stats_data = $data['entry']['yt$statistics'];$medya = $data['entry']['media$thumbnail'];//yt$username kısmından kanal adı parse edilir/**********************************************************/echo "<img src='$medya[url]'></img><br>";echo "Subscribers: $stats_data[subscriberCount]<br>";echo "Views: $stats_data[totalUploadViews]<br>";