Login with Google Account

Database
Sample database users table columns id, email, oauth_uid, oauth_provider and username.

CREATE TABLE users
(
id INT PRIMARY KEY AUTO_INCREMENT,
email VARCHAR(70), 
oauth_uid int(11),
oauth_provider VARCHAR(100),
username VARCHAR(100) 
);

In this tutorial we have the following directory structure

google-open //Google LightOpenID library
config
-- functions.php 
-- dbconfig.php //Database connection
index.php
home.php
getGoogleData.php //The Callback URL file
login-google.php

dbconfig.php
Database configuration file. 

<?php

define('DB_SERVER', 'dbserver');
define('DB_USERNAME', 'username');
define('DB_PASSWORD', 'password');
define('DB_DATABASE', 'database');

define('USERS_TABLE_NAME', 'users_table_name'); //Replace your users table name here
$connection = mysql_connect(DB_SERVER, DB_USERNAME, DB_PASSWORD) ordie(mysql_error());
$database = mysql_select_db(DB_DATABASE) or die(mysql_error());
?>

login-google.php
In root directory find out the below line at login-google.php code and replaceyourdomain.com with your own domain  value. 

define('CALLBACK_URL', 'http://yourdomain.com/getGoogleData.php');

index.php
If you want to modify your web project existing login or index pages, just use following code. 

<?php
session_start();
if (isset($_SESSION['id'])) {
// Redirect to home page as we are already logged in
header("location: home.php");
}
if (array_key_exists("login", $_GET)) 
{
$oauth_provider = $_GET['oauth_provider'];
if ($oauth_provider == 'google')
{
header("Location: login-google.php");
}
}
?>
//HTML Code
<a href="?login&oauth_provider=google">Google Login</a>

home.php
In home page you can display user details by accessing session variables.

Name: <?php $_SESSIONS['username'] >
Email: <?php $_SESSIONS['email'] >
Your are logged in with: <?php $_SESSIONS['oauth_provider'] >
<a href="logout.php?logout">Logout</a> from  <?php $_SESSIONS['oauth_provider'] >

If any queries please comment here.