How to share google docs using oauth in php

Question

I need to change my AuthSub code to oAuth since Google is deprecating AuthSub. In my project currently a user can create and share his google docs to other with writer/read only role.

While changing authsub to oauth, I am able to create new docs with oauth code, but I am not able to share this docs to other user.

Here is my authsub code

<?php 

$dataShare="<feed xmlns=\"w3.org/2005/Atom\" xmlns:gAcl='schemas.google.com/acl/2007'; xmlns:batch='schemas.google.com/gdata/batch'>; <category scheme='schemas.google.com/g/2005#kind'; term='schemas.google.com/acl/2007#accessRule'/>";;

$dataShare .= "<entry> 
                    <batch:id>1</batch:id> 
                    <batch:operation type='insert'/> 
                    <gAcl:role value='writer' /> 
                    <gAcl:scope type='user' value='emailid@gmail.com'/> </entry>"; 
$dataShare .= "</feed>"; 

$uri = "docs.google.com/feeds/default/private/full/$newShareDocID/acl/batch";
$headers[]= "Host: docs.google.com"; 
$headers[]= "GData-Version: 3.0"; 
$headers[]= "Content-Type: application/atom+xml"; 
$headers[]= "Authorization: AuthSub token=\"".$_SESSION['docsSampleSessionToken']."\""; 
$a = new cURL($headers); 
$b = $a->post($uri, $dataShare); 

?>

How do I change this sharing code according to oauth. I searched on net but couldn't find anything. Thanks in advance..