Using graph api:
function getUserFriendList($facebook){
        $friends     =   $facebook->api('/me/friends');
        return $friends;
}



Using legacy api:
function getUserFriendList($facebook, $uid){
    try {
        $param  =   array(
                'method'  => 'friends.get',
                'uid'     => $uid,
                'flid'    => '',
                'callback'=> ''
        );
        $friends   =   $facebook->api($param);
        return $friends;
    }
    catch(Exception $o) {
        d($o);
    }
    return '';
}

http://thinkdiff.net/facebook/how-to-retrieve-facebook-users-friendlist/

How to retrieve facebook user’s friendlist

list, api, facebook

PHP