How to set cookies ONLY on the main domain?

Question

PHP

When setting cookies:
setcookie("Data", $data, 0, "/", "example.com");
they still extend to subdomains. How can I make sure that these cookies are only on the main domain?
Note:
In RFC 2109, a domain without a leading dot meant that it could not be used on subdomains, and only a leading dot ( .mydomain.com ) would allow it to be used on subdomains.
However, modern browsers respect the new RFC 6265 specification and ignore any leading dot, which means you can use a cookie on subdomains as well as top level domains.
So if you set a cookie like the second example above from mydomain .com , it will be available for subdomain.mydomain.com and vice versa.

Answer 1

do not specify domain at all in setcookie, then it will not work on subdomains:
setcookie("Data", $data, 1, "/");