如何通过谷歌验证用户使用php发送电子邮件？

在我的web应用程序中，用户可以使用他们的gmail帐户登录到该站点[我是通过Oauth实现的]。现在，我想使用登录用户的gmail帐户从我的应用程序向其他用户发送电子邮件。这怎么可能呢

My simple index.php

<?php

  session_start();

  require_once 'google-api-php-client-master/src/Google/Client.php';
  require_once 'google-api-php-client-master/src/Google/Service/Gmail.php';

  // Replace this with you/r Google Client ID

  $client_id     = 'client id';
  $client_secret = 'client secret';
  $redirect_uri  = 'https://localhost/mail/index.php'; // Change this
  $server_key='server key';

  $client = new Google_Client();
  $client->setApplicationName("Mail sending application");
  $client->setClientId($client_id);
  $client->setClientSecret($client_secret);
  $client->setRedirectUri($redirect_uri);
  $client->setDeveloperKey($server_key);

  // We only need permissions to compose and send emails
  $client->addScope("https://www.googleapis.com/auth/gmail.compose");
  $service = new Google_Service_Gmail($client);

  // Redirect the URL after OAuth
  if (isset($_GET['code'])) {
    $client->authenticate($_GET['code']);
    $_SESSION['access_token'] = $client->getAccessToken();
    $redirect = 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF'];
    header('Location: ' . filter_var($redirect, FILTER_SANITIZE_URL));
  }

  // If Access Toket is not set, show the OAuth URL
  if (isset($_SESSION['access_token']) && $_SESSION['access_token']) {
    $client->setAccessToken($_SESSION['access_token']);
  } else {
    $authUrl = $client->createAuthUrl();
  }

  if ($client->getAccessToken() && isset($_POST['message'])) {

    $_SESSION['access_token'] = $client->getAccessToken();

    // Prepare the message in message/rfc822
    try {

        // The message needs to be encoded in Base64URL
        $mime = rtrim(strtr(base64_encode($_POST["message"]), '+/', '-_'), '=');
        $msg = new Google_Service_Gmail_Message();
        $msg->setRaw($mime);
        $service->users_messages->send("me", $msg);

    } catch (Exception $e) {
        print($e->getMessage());
        unset($_SESSION['access_token']);
    }

  } ?>

 <?php if ( isset ( $authUrl ) ) { ?>
  <a href="<?php echo $authUrl; ?>">sign in</a>
 <?php } else { ?>
  <form method="POST" action="">
    <textarea name="message" required></textarea>
    <input type="email" required name="to">
    <input type="text"  required name="subject">
    <a href="#" onclick="document.forms.htmlmail.submit();return false;">Send Mail</a>
  </form>
<?php } ?>

从谷歌查询。这是正在发送的邮件

还有一个可用的测试版

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检查此代码示例。 检查此选项，了解有关此主题的讨论

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使用phpmailer或php的默认邮件（）的措辞稍微好一点。我正在使用google api进行身份验证，我知道同样的库也可以用于邮件目的。如果可能的话，请告诉我代码我没有使用zend框架。我正在使用codeigniter@SandhyaGor检查

Error: invalid_client

no support email

Request Details
from_login=1
response_type=code
scope=https://www.googleapis.com/auth/gmail.compose
redirect_uri=https://localhost/mail/index.php
access_type=online
approval_prompt=auto
as=-4de25f3b2be1f07c
client_id=570442960066-01d3mblkltjfjjt9ivnqiki5vvanlas9.apps.googleusercontent.com
hl=en