php cookie variables

I was wondering how to set and retrieve information from a cookie, where the information retrieved will be modified by a variable, for example if the cookie is 1, i want the next cookie to be 2, so can I add "+1"?

For example:

<?php
setcookie("count","1");
?>

and when the cookie is read I want to do like this:
<?php
if (isset($_COOKIE["count"]))
echo "new number" . $_COOKIE["count"]+1 . "!<br />";
else
echo "no numbers to add!<br />";
?>

 

if (isset($_COOKIE["count"])) {
$_COOKIE["count"]++;
}