I have found the solution though with a little overheads. Steps are: 1> Create a PHP script in you own server (say named, YRedirect.php). 2> Paste the following code in it-
CODE
<?php
$query = $_SERVER['QUERY_STRING'];
header("Location: com-mycompany-myapp://oauth-response?" . $query);
>
Where "com-mycompany-myapp" is your bundle identifier
3> Add an URL Scheme in your info.plist file with the YOUR_APP_ID_OR_BUNDLE_ID. That's it and you are DONE with the authentication problem.
In your code
[self.session sendUserToAuthorizationWithCallbackUrl:@"http://yourdomain.com/YRedirect.php"];
Then, register a custom URL scheme for your iPhone application from your Info.plist file, and then setup your server side script to redirect Safari back to your application via the URL scheme you just set up.
Thanks for this valuable information. Following your instructions I got the auth & call back working and the php page loads the app.