Twitter代码“Not Fol Back”PHP

I have this code, to get followers and friends(peeps you are following), However I'm completely lost, I want to get a "Who's not following back" page. Whats the best way to go about this? Should I manually search for strings or . . .

Pseudo :: $riends-$followers

$user = $query[1];
    if (!$user) {
        user_ensure_authenticated();
        $user = user_current_username();
    }
    $folwers = API_URL."statuses/followers/{$user}.xml";
    $folwin = API_URL."statuses/friends/{$user}.xml";

    $tl = lists_paginated_process($request);
    $content = theme('followers', $tl);
    theme('page', 'Followers', $content);
}

Thanks

This might not be the most optimal answer out there, but you might want to read the following link:

https://dev.twitter.com/docs/api/1/get/friendships/exists

Since you're able to get all profiles that you're following, you could easily just loop the array of usernames and curl to the "friendship verification"-page. Check out the snippet below:

<?php 
    $link = 'http://api.twitter.com/1/friendships/exists.xml?screen_name_a=php_net&screen_name_b=';   
    foreach( $usernames as $username ) {

        //Create a curl handler and make sure we return to a variable
        $ch = curl_init($link . $username);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        $status = strip_tags(curl_exec($ch)); //Should return: true
        curl_close($ch);

        //Output based on the results
        if( $status == 'true' ) echo $username , ' isn\'t following you. <br />';
        else echo $username , ' is following you. <br />';
    }
?>

It might at least be worth a shot, although I'm pretty sure that there are better ways to accomplish what you're looking for. Good luck!