function ClickThrough(ct_url, user_id) {
    this.ct_url = ct_url;
    this.user_id = user_id;

    this.clickthrough = function (click_index, redirect) {

	    var params = { "click_index": click_index };
	    if (this.user_id) {
	    	params.user_id = this.user_id;
	    }

        $.post( 'ct.php', params,
            function(data) {
                window.location = redirect;
            }, "text" );

    };

    this.track = function (stage) {
	    var params = {"stage":stage};

	    $.post( 'track.php', params,
            function(data) {
                
            }, "text" );
    };
}