Gmail Push Notification | Gmail callback webhook setup step by step guide

┌─────────────┐      ┌─────────────┐      ┌─────────────┐      ┌─────────────┐
│             │      │             │      │             │      │             │
│   Gmail     │─────▶│  Pub/Sub    │─────▶│  Webhook    │─────▶│   OTP Log   │
│   Inbox     │      │   Topic     │      │   (PHP)     │      │   / Verify  │
│             │      │             │      │             │      │             │
└─────────────┘      └─────────────┘      └─────────────┘      └─────────────┘
      │                     │                     │                     │
      │                     │                     │                     │
      ▼                     ▼                     ▼                     ▼
  New Email        Push Notification    process_latest_email    email_content.log

cd /path/to/your/project
composer require google/apiclient

<?php
// watch_gmail.php - OAuth 2.0 Web Application
require_once 'vendor/autoload.php';

use Google_Client;
use Google_Service_Gmail;
use Google_Service_Gmail_WatchRequest;

// ============ कॉन्फ़िगरेशन ============
define('MY_EMAIL', '[email protected]');        // अपना Gmail ID
define('PROJECT_ID', 'your-project-id');           // Google Cloud Project ID
define('TOPIC_NAME', 'gmail-otp-topic');           // Pub/Sub Topic Name
define('CLIENT_SECRET_FILE', 'client_secret.json');
define('TOKEN_FILE', 'token.json');
// ========================================

function getClient() {
    $client = new Google_Client();
    $client->setAuthConfig(CLIENT_SECRET_FILE);
    $client->setScopes(['https://mail.google.com/']);
    $client->setAccessType('offline');
    $client->setPrompt('consent');
    return $client;
}

// 1. OAuth Callback - Code से Token बनाएँ
if (isset($_GET['code'])) {
    $code = $_GET['code'];
    $client = getClient();
    try {
        $accessToken = $client->fetchAccessTokenWithAuthCode($code);
        if (isset($accessToken['error'])) {
            throw new Exception($accessToken['error_description'] ?? 'Unknown error');
        }
        file_put_contents(TOKEN_FILE, json_encode($accessToken));
        echo "✅ Authorization Successful! Token saved.<br>";
        echo "🔄 अब आप watch_gmail.php को बिना ?code= के Run करें।";
        exit;
    } catch (Exception $e) {
        die("❌ Error: " . $e->getMessage());
    }
}

// 2. Token मौजूद है - Watch शुरू करें
if (file_exists(TOKEN_FILE)) {
    $client = getClient();
    $accessToken = json_decode(file_get_contents(TOKEN_FILE), true);
    $client->setAccessToken($accessToken);

    // Token Expire हो तो Refresh
    if ($client->isAccessTokenExpired()) {
        $refreshToken = $client->getRefreshToken();
        if ($refreshToken) {
            $newToken = $client->fetchAccessTokenWithRefreshToken($refreshToken);
            file_put_contents(TOKEN_FILE, json_encode($client->getAccessToken()));
        } else {
            unlink(TOKEN_FILE);
            header('Location: ' . filter_var($client->createAuthUrl(), FILTER_SANITIZE_URL));
            exit;
        }
    }

    $service = new Google_Service_Gmail($client);

    try {
        $watch = new Google_Service_Gmail_WatchRequest();
        $watch->setTopicName("projects/" . PROJECT_ID . "/topics/" . TOPIC_NAME);
        $response = $service->users->watch(MY_EMAIL, $watch);
        $expiry = $response->getExpiration() / 1000;
        echo "\n✅ Watch Setup Successful!\n";
        echo "📅 Expires at: " . date('Y-m-d H:i:s', $expiry) . "\n";
        echo "🔄 इसे हर 7 दिन में Renew करें (Cron Job).\n";
    } catch (Exception $e) {
        echo "\n❌ Error: " . $e->getMessage() . "\n";
        echo "💡 अगर Error आए, तो token.json डिलीट करें और watch_gmail.php को बिना ?code= के Run करें।\n";
    }
    exit;
}

// 3. Token नहीं है - Google Login पर Redirect
$client = getClient();
$authUrl = $client->createAuthUrl();
header('Location: ' . filter_var($authUrl, FILTER_SANITIZE_URL));
exit;
?>

<?php
// gmail_webhook.php - Pub/Sub से POST पढ़े और Log करे
$logFile = __DIR__ . '/pubsub_callback_log.txt';
$rawInput = file_get_contents('php://input');
$headers = getallheaders();

$logEntry = [
    'timestamp' => date('Y-m-d H:i:s'),
    'remote_ip' => $_SERVER['REMOTE_ADDR'] ?? 'unknown',
    'headers'   => $headers,
    'raw_input' => $rawInput,
    'decoded'   => json_decode($rawInput, true)
];

$logLine = json_encode($logEntry, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES) . "\n\n---\n\n";
file_put_contents($logFile, $logLine, FILE_APPEND | LOCK_EX);

// OTP Processing Trigger
$data = json_decode($rawInput, true);
if (isset($data['message']['data'])) {
    $messageData = base64_decode($data['message']['data']);
    $gmailEvent = json_decode($messageData, true);
    if (isset($gmailEvent['historyId'])) {
        file_put_contents(
            __DIR__ . '/otp_trigger.log',
            date('Y-m-d H:i:s') . " - historyId: " . $gmailEvent['historyId'] . PHP_EOL,
            FILE_APPEND
        );
        // Background में process_latest_email.php चलाएँ
        shell_exec("php " . __DIR__ . "/process_latest_email.php >> /dev/null 2>&1 &");
    }
}

http_response_code(200);
echo 'OK';
?>

<?php
// process_latest_email.php - नवीनतम मेल का कंटेंट लॉग करें
require_once 'vendor/autoload.php';

use Google_Client;
use Google_Service_Gmail;

define('MY_EMAIL', '[email protected]');
define('TOKEN_FILE', 'token.json');
define('CLIENT_SECRET_FILE', 'client_secret.json');
define('LOG_FILE', __DIR__ . '/email_content.log');

function getGmailService() {
    $client = new Google_Client();
    $client->setAuthConfig(CLIENT_SECRET_FILE);
    $client->setScopes(['https://mail.google.com/']);
    $client->setAccessType('offline');

    if (file_exists(TOKEN_FILE)) {
        $accessToken = json_decode(file_get_contents(TOKEN_FILE), true);
        $client->setAccessToken($accessToken);
    }

    if ($client->isAccessTokenExpired()) {
        $refreshToken = $client->getRefreshToken();
        if ($refreshToken) {
            $newToken = $client->fetchAccessTokenWithRefreshToken($refreshToken);
            file_put_contents(TOKEN_FILE, json_encode($client->getAccessToken()));
        } else {
            die("❌ Refresh Token नहीं मिला।\n");
        }
    }
    return new Google_Service_Gmail($client);
}

function htmlToPlainText($html) {
    $text = strip_tags($html);
    $text = html_entity_decode($text, ENT_QUOTES | ENT_HTML5, 'UTF-8');
    $text = preg_replace('/\s+/', ' ', $text);
    return trim($text);
}

function getEmailBody($payload) {
    $plain = ''; $html = '';
    if ($payload->getMimeType() == 'text/plain') {
        $data = $payload->getBody()->getData();
        if ($data) $plain = base64_decode(str_replace(['-', '_'], ['+', '/'], $data));
    } elseif ($payload->getMimeType() == 'text/html') {
        $data = $payload->getBody()->getData();
        if ($data) $html = base64_decode(str_replace(['-', '_'], ['+', '/'], $data));
    } elseif (strpos($payload->getMimeType(), 'multipart/') === 0) {
        foreach ($payload->getParts() as $part) {
            $result = getEmailBody($part);
            if ($result['plain']) $plain = $result['plain'];
            if ($result['html']) $html = $result['html'];
        }
    }
    return ['plain' => $plain, 'html' => $html];
}

$service = getGmailService();

try {
    $optParams = ['maxResults' => 1, 'q' => 'in:inbox'];
    $messages = $service->users_messages->listUsersMessages('me', $optParams);
    if (count($messages->getMessages()) == 0) {
        file_put_contents(LOG_FILE, date('Y-m-d H:i:s') . " - No new emails.\n", FILE_APPEND);
        echo "📭 Inbox empty.\n";
        exit;
    }

    $msgId = $messages->getMessages()[0]->getId();
    $message = $service->users_messages->get('me', $msgId, ['format' => 'full']);

    $subject = $from = '';
    foreach ($message->getPayload()->getHeaders() as $header) {
        if ($header->getName() == 'Subject') $subject = $header->getValue();
        if ($header->getName() == 'From') $from = $header->getValue();
    }

    $body = getEmailBody($message->getPayload());
    $plainText = $body['plain'] ?: htmlToPlainText($body['html']);

    $logContent = "========================================\n";
    $logContent .= "📅 Time: " . date('Y-m-d H:i:s') . "\n";
    $logContent .= "📩 From: " . $from . "\n";
    $logContent .= "📌 Subject: " . $subject . "\n";
    $logContent .= "📝 Body:\n" . $plainText . "\n";
    $logContent .= "========================================\n\n";

    file_put_contents(LOG_FILE, $logContent, FILE_APPEND);
    echo "✅ Email logged.\n";

} catch (Exception $e) {
    file_put_contents(LOG_FILE, date('Y-m-d H:i:s') . " - Error: " . $e->getMessage() . "\n", FILE_APPEND);
    echo "❌ Error: " . $e->getMessage() . "\n";
}
?>

php /path/to/your/project/watch_gmail.php

✅ Watch Setup Successful!
📅 Expires at: 2026-09-13 14:02:40
🔄 इसे हर 7 दिन में Renew करें (Cron Job).

crontab -e

0 6 * * * php /path/to/your/project/watch_gmail.php >> /var/log/gmail_watch_renew.log 2>&1

/public_html/project/
├── client_secret.json              # GCP से Download की गई JSON
├── token.json                      # Auto-generated (कभी Delete न करें)
├── watch_gmail.php                 # Cron वाली फाइल
├── gmail_webhook.php               # Pub/Sub Endpoint
├── process_latest_email.php        # Email Reader
├── vendor/                         # Composer Libraries
├── email_content.log               # मेल कंटेंट (Auto-generated)
├── otp_trigger.log                 # historyId Log (Auto-generated)
└── pubsub_callback_log.txt         # Pub/Sub POST Log (Auto-generated)