Pekka's comment should be an answer. The string parameter after the hash tag is not sent to the server, it's for the browsers eyes only.
This means that serverside code (PHP, in your case) does not have this info. The clientside code (the browser, javascript, ...) does.
Ideally,
- the part after the ? is info for the server. Put everything your
server needs here
- the part after the # is info for the client. Put everything your
client needs here. It's called the Fragment Identifier (Thanks Tim).
Historically, the part after the # was most often used to have your browser quicky scroll to a defined anchor on the page. Nowadays, it is more often used to hold state information for the client.
You could have javascript send this info to the server, or perform different actions based on this info. AJAX is your friend.
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