When setCookie () is used, the Cookie cannot be saved if the domain name is specified as "localhost". why?

When setCookie () is used, the Cookie cannot be saved if the domain name is specified as "localhost". why ?? Found during local testing. In this way, you can set the Cookie: PHPcodesetCookie ('name [1] ', 'yy1', time () + 3600,' when setCookie () is used, when the domain name is specified as "localhost", the Cookie cannot be saved. why ??
Found during local testing.

In this way, you can set the Cookie:

PHP code

      setCookie('name[1]', 'yy1', time() + 3600, '/');    setCookie('name[2]', 'yy2', time() + 3600, '/');

This will not work:

PHP code

      setCookie('name[1]', 'yy1', time() + 3600, '/', 'localhost');    setCookie('name[2]', 'yy2', time() + 3600, '/', 'localhost');

Why? Is the parameter "localhost" incorrect ???

Thank you!

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When working on localhost the cookie-domain must be set to "" or NULL or FALSE
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Discussion

When working on localhost the cookie-domain must be set to "" or NULL or FALSE