Google Login Integration with PHP — OAuth Implementation Guide

1. Overview
Integrating Google Login allows you to implement user authentication quickly and securely, without managing passwords yourself.

2. Prerequisites

Access the Google Cloud Console
Create an OAuth client
Obtain a Client ID (and Client Secret)


3. Login Flow
User clicks "Login with Google"
↓
Google authentication screen
↓
Redirected to callback.php
↓
Receive user information from Google
↓
Save to session

4. Initiating the Login Request
phpheader("Location: https://accounts.google.com/o/oauth2/auth?" . http_build_query([
'client_id' => YOUR_CLIENT_ID,
'redirect_uri' => 'https://yoursite.com/callback.php',
'response_type' => 'code',
'scope' => 'email profile',
]));

5. Handling the Callback
php// After verifying the token and retrieving user info from Google:
$_SESSION['user_id'] = $user['id'];
$_SESSION['username'] = $user['name'];

6. Saving the User to the Database
sqlINSERT INTO users (google_id, username, email)
VALUES (?, ?, ?)

7. Checking Login Status
phpfunction is_logged_in() {
return isset($_SESSION['user_id']);
}

8. Summary

Authentication is handled via the OAuth 2.0 protocol
The key step is saving the session inside the callback handler
Connecting to a database enables full user account management


💡 Pro Tip
Google Login offers the best of both worlds — strong security and user convenience — by letting Google handle credential verification so you don't have to store or manage passwords directly.