How do you update a cookie in PHP?

问题:

If I call setcookie() two times with the same cookie name, I get two cookies created.

How do you update an existing cookie?

回答1:

You can't update a cookie per se, you can however overwrite it. Otherwise, this is what you are looking for: http://php.net/manual/en/function.setcookie.php

It works. Be sure to read "Common Pitfalls" from that page.

You can use the super global $_COOKIE['cookie_name'] as well to read/write cookies.

回答2:

You can update a cookie value using setcookie() function, but you should add '/' in the 4th argument which is the 'path' argument, to prevent creating another cookie with the same name.

i.e. setcookie('cookie_name', 'cookie_value', $exp_date, '/');

回答3:

So while PHP will send two Set-Cookie: headers if instructed so, only the last one should persist in browsers.
The Netscape cookie spec http://curl.haxx.se/rfc/cookie_spec.html says:

Instances of the same path and name will overwrite each other, with the latest instance taking precedence. Instances of the same path but different names will add additional mappings.

However, it might be advisable to avoid such edge conditions. Restructure your application so it doesn't need to override the already sent cookie.

回答4:

call COOKIE and delete username value SETCOOKIE("username",'',0,"/");