如何使用此方法获取google plus配置文件的封面图片链接？

Question

我最近关注了如何使用google进行身份验证的教程

他们使用此方法来提取数据

 echo '<div class="welcome_txt">Welcome <b>'.$_SESSION['google_data']['given_name'].'</b></div>';
echo '<div class="google_box">';
echo '<p class="image"><img src="'.$_SESSION['google_data']['picture'].'" alt="" width="300" height="220"/></p>';
echo '<p><b>Google ID : </b>' . $_SESSION['google_data']['id'].'</p>';
echo '<p><b>Name : </b>' . $_SESSION['google_data']['name'].'</p>';
echo '<p><b>Email : </b>' . $_SESSION['google_data']['email'].'</p>';
echo '<p><b>Gender : </b>' . $_SESSION['google_data']['gender'].'</p>';
echo '<p><b>Locale : </b>' . $_SESSION['google_data']['locale'].'</p>';
echo '<p><b>Google+ Link : </b>' . $_SESSION['google_data']['link'].'</p>'

通过使用此方法如何拉封面图片。帮助我

index.php

<?php 

include_once("config.php");
include_once("includes/functions.php");

//print_r($_GET);die;

if(isset($_REQUEST['code'])){
  $gClient->authenticate();
  $_SESSION['token'] = $gClient->getAccessToken();
  header('Location: ' . filter_var($redirect_url, FILTER_SANITIZE_URL));
}

if (isset($_SESSION['token'])) {
  $gClient->setAccessToken($_SESSION['token']);
}

if ($gClient->getAccessToken()) {
  $userProfile = $google_oauthV2->userinfo->get();
  //DB Insert
  $gUser = new Users();
  $gUser->checkUser('google',$userProfile['id'],$userProfile['given_name'],$userProfile['family_name'],$userProfile['email'],$userProfile['gender'],$userProfile['locale'],$userProfile['link'],$userProfile['picture']);
  $_SESSION['google_data'] = $userProfile; // Storing Google User Data in Session
  header("location: feed.php");
  $_SESSION['token'] = $gClient->getAccessToken();
} else {
  $authUrl = $gClient->createAuthUrl();
}

?>