How can I read these Apache HTTP Headers using PHP before they’re sent to the client’s browser?

HTTP/1.1 200 OK
Last-Modified: Sun, 09 Jul 2023 09:41:38 GMT
Expires: Mon, 10 Jul 2023 07:20:55 GMT
Cache-Control: private, max-age=0
Date: Mon, 10 Jul 2023 07:20:55 GMT
Content-Type: application/json; charset=UTF-8
Content-Length: 2561