php - Post tweet to a user with Twitter API

Question

I have been using the Twitter Oauth API for posting tweets to my twitter timeline from my php application. It is working well.

<?php
$tweet = new TwitterOAuth($consumerKey, $consumerSecret, $OAuthToken, $OAuthSecret);
$message = "This is a test message.";
$tweet->post('statuses/update', array('status' => "$message"));
?>

But i would like to know, is there an API that can post tweets to the timeline of my friends (those i am following on twitter) ? Or does the twitter API allow posting of tweets only to the authenticated user's timeline?