删除cookie不起作用

hello i`m running crazy through a problem that i tried to fetch.

i can not delete a cookie that will be set on index.php like that:

$a = 'text';
setcookie('name_of_cookie', $a, time()+60*60*24*365);

on page-php i can call that cookie and the content is like $a. i tried to delete that different ways on page.php like that:

setcookie('name_of_cookie', FALSE, time()-3600);

i also found a version where i only set it to:

setcookie('name_of_cookie');

what just will set a another cookie with the same name like i saw in the settings of the browser. that new cookie has no content - sure, there is no content declared.

i also tried to set a higher time in the past because of the server location but this doesnt work as well. even trying to set the time to just 1 does not work.

i checked the spelling of the name sveral times, there is no failure that comes from different names.

i would be glad if someone could tell what am i doing wrong?

thanks.