如何使用php facebook sdk获取用户的电子邮件

Question

我正在使用php facebook graph api登录facebook，在这里登录facebook后我得到了用户的详细信息，如姓名，身份证，位置，链接。但我无法获得用户的电子邮件ID。我提到了很多这样的例子，但我无法理解如何在我的代码中做到这一点。

这是我的代码：

<?php

/* INCLUSION OF LIBRARY FILEs*/
	require_once( 'lib/Facebook/FacebookSession.php');
	require_once( 'lib/Facebook/FacebookRequest.php' );
	require_once( 'lib/Facebook/FacebookResponse.php' );
	require_once( 'lib/Facebook/FacebookSDKException.php' );
	require_once( 'lib/Facebook/FacebookRequestException.php' );
	require_once( 'lib/Facebook/FacebookRedirectLoginHelper.php');
	require_once( 'lib/Facebook/FacebookAuthorizationException.php' );
	require_once( 'lib/Facebook/GraphObject.php' );
	require_once( 'lib/Facebook/GraphUser.php' );
	require_once( 'lib/Facebook/GraphSessionInfo.php' );
	require_once( 'lib/Facebook/Entities/AccessToken.php');
	require_once( 'lib/Facebook/HttpClients/FacebookCurl.php' );
	require_once( 'lib/Facebook/HttpClients/FacebookHttpable.php');
	require_once( 'lib/Facebook/HttpClients/FacebookCurlHttpClient.php');

/* USE NAMESPACES */
	
	use Facebook\FacebookSession;
	use Facebook\FacebookRedirectLoginHelper;
	use Facebook\FacebookRequest;
	use Facebook\FacebookResponse;
	use Facebook\FacebookSDKException;
	use Facebook\FacebookRequestException;
	use Facebook\FacebookAuthorizationException;
	use Facebook\GraphObject;
	use Facebook\GraphUser;
	use Facebook\GraphSessionInfo;
	use Facebook\FacebookHttpable;
	use Facebook\FacebookCurlHttpClient;
	use Facebook\FacebookCurl;

/*PROCESS*/
	session_start();
	
	 $app_id = '389605751141082';
	 $app_secret = 'a59a6fb216eafe5e3accc7b95f53c3bc';
	 $redirect_url='http://parshwatax.com/november/facebook/test.php';
	 
	
	 FacebookSession::setDefaultApplication($app_id,$app_secret);
	 $helper = new FacebookRedirectLoginHelper($redirect_url);
	 $sess = $helper->getSessionFromRedirect();
      
if(isset($sess)){
                $request = new FacebookRequest($sess, 'GET', '/me');
	$response = $request->execute();
               $graph = $response->getGraphObject(GraphUser::className());
           
                $fname= $graph->getFirstName();
               echo "hi $fname";
                 $lname= $graph->getLastName();
               echo "$lname"; 
                $id= $graph->getId();
               echo "$id";
               $link= $graph->getLink();
               echo "$link";
              $mail= $graph->getEmail();
               echo "$mail";

require_once("connection.php");
$q="select * from `myuser` where `Email`='$mail'";
$r=mysql_query($q);
$row=mysql_fetch_assoc($r);
$uid=$row['Userid'];
echo $uid;
echo "Your are successfully login <a href='http://parshwatax.com/november/fblogincheck.php?a=$uid'>click here</a> to enjoy swapping...!";
}
?>

这是页面的主要部分，我不清楚，但我只需要电子邮件ID。