Cookies Are Headers

Learn more about cookies.

Set-Cookie header and Cookie header

Personally, I’ve had a lot of trouble understanding cookies and how to use them correctly. That’s because I didn’t realize they were headers. When you call setcookie(), the result is not some magic cookie (whatever that is), but a Set-Cookie response header. Only when the browser has received the response from the server, it will process the Set-Cookie headers of the response and keep the provided values in its own storage facility. The next time it makes a request to your server, it will look in that same storage facility for any cookies that should be sent to the server as a Cookie header on the request. The following diagram illustrates this process of setting a cookie and getting that cookie in the next request:

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