Getting a 401 Error when trying to DELETE


I am authenticating on every API call apart from DELETE.
Can anyone shed some light on why this code I use for all my other applications fails on a 401 error when trying to unfollow somone. Using the same method to pull in followers, tweets etc is working great.

<?php require '../include/tmhOAuth.php'; require '../include/tmhUtilities.php'; $tmhOAuth = new tmhOAuth(array( 'consumer_key' => '***HIDDEN******', 'consumer_secret' => '***HIDDEN******', 'user_token' => '***HIDDEN******', 'user_secret' => '***HIDDEN******', )); $user_id = 13; $tmhOAuth->request('DELETE', $tmhOAuth->url('1/friendships/destroy'), array( 'user_id' => $user_id )); echo $tmhOAuth->response['code']; ?>