One of the common scenarios is to login through an external account like Google+, Twitter or Facebook.
In this code snippet I will show how to login using Google+ API
First you need to register your api at https://code.google.com/apis/console/, register the Google+ API Service and create a new application; in the “Redirect URI” you need to pass the path of the script and add the following: “googleplus.php?op=redirect” I will comment why is this later, after you see the code, you can fragment code into other more elegant paths/scripts.
From the generated application you will need the Redirection URI and the Client ID
Google OAuth works in the following way:
- Generate an URL using params of services you want to access (
scope) and your Client ID and Redirection URI - You need to redirect user to this URL
- After user has approved the use, you will be redirected with a hash params, so your server won’t see it, you can pass to your server through ajax or in this case through a GET request
In the code the “?op=redirect” will show just a white page with a javascript redirection to convert the hash location into a normal GET request; this will enable in the server to grab the access_token which you can use to verify through Google+ site if is valid.
This code part does it:
<?php
$access_token = $_GET['access_token'];
//do something with the token, first check is real
$data = @file_get_contents("https://www.googleapis.com/plus/v1/people/me?access_token={$access_token}");
if ($data) {
print $data;
} else {
print "Token not valid!";
}
The code is not prepared to handle error (will show as a $_GET['error'] after have redirected) so you need to handle that for your scenario.
Links:
- https://github.com/danguer/blog-examples/blob/master/php/oauth/googleplus.php (Code to authenticate)
- https://code.google.com/apis/accounts/docs/OAuth2.html (Google OAuth implementation)
- https://developers.google.com/+/api/ (Google+ API)
