php for am-i-logged-in

am-i-logged-in.php

    public function am_i_logged_in() {

        if(!IS_AJAX) {
            echo 'Hi there!<br><br>In case you were wondering - the address that you\'ve just visited is used by us to check if you\'re still logged into GatherContent, and if, by any chance, your browser logs you out - we will display information within the app to prevent data loss!';
            exit;
        }

        $json = array();

        if(!$u = Current_User::user()) {
            $json['success'] = false;
        }
        else {
            if(isset($u->id) && $u->id != 0) {
                $json['success'] = true;
            }
            else {
                $json['success'] = false;
            }  
        }

        echo json_encode($json);

        exit;

    }