Tweet from website using PHP



I am trying to develop a web page which would allow a user to log in and send a tweet to their account, from that webpage.

This is the code I have so far -

// Include twitteroauth

// Set keys

// Create object
$tweet = new TwitterOAuth($consumerKey, $consumerSecret, $accessToken, $accessTokenSecret);

// Set status message
$tweetMessage = 'Twitter :D';

// Check for 140 characters
if(strlen($tweetMessage) <= 140)
    // Post the status message
    $tweet->post('statuses/update', array('status' => $tweetMessage));
    echo "Tweet Posted";

This code is hard coded to send tweets through my account. My question is, how can I modify this to authenticate a user and post tweets to his account? (I’m guessing I shouldn’t hard code all the 4 keys, but I’m not sure).

Any guidance here is largely appreciated!