Hello everyone and thanks much for your past help, especially printf!

I am still working on adding multiple values to a cookie through several checkboxes on a Classified Advertisements page. I have the checkboxes beside each classified advertisement so the user can click a submit button and Add to My Classifieds and keep track of only the classified ads they want to view and print. The name of the checkboxes are _Check and the value of each checkbox is the Ad Number. So I am trying to obtain all of the Ad Numbers the visitor clicks on and pass those values to a cookie so that I can pull only those ads on a separate My Classifieds page.

In the following code, the problem I am having is if the cookie is already set, taking the Ad Numbers already found in the cookie and unserializing them, then re-serializing them within the cookie and serializing the new Ad Numbers the visitor has clicked on. Basically, the cookie needs to always keep the existing Ad Numbers and the new Ad Numbers. I'm just not sure how to accomplish this, so any input would be much appreciated. Thanks!

Code:
<?php
if (isset($_POST['_Check']))
{
        $items  = '';
	$items2 = '';
	$items3 = '';
	$items4 = '';
	
    if (isset($_COOKIE['AddMyClass']))
    {
                $items = explode('|', unserialize($_COOKIE['AddMyClass']));
		$items2 = implode('|', $items);
		$items3 = serialize($items2);
		$items4 = serialize(implode('|', $_POST['_Check']));
		setcookie ('AddMyClass', $items3 . $items4, (time() + 31536000));
	}
	else
	{
   		setcookie ('AddMyClass', serialize(implode('|',$_POST['_Check'])), (time() + 31536000));
	}	

}
	
	if (isset($_COOKIE['AddMyClass']))
	{
		echo unserialize($_COOKIE['AddMyClass']);
	}
?>