how do I use the getwalletinfo RPC? I can't seem to get a firm grasp of how to use the getwalletinfo RPC in the cmd line as well as in PHP code, The documentation says getwalletinfo doesn't take any parameters, but I've seen ways to send specific requests to the daemon this RPC. So, my question is, how do I use the getwalletinfo RPC in PHP to get information of a specific wallet?
getwalletinfo does not take parameters.

It sounds like what you are looking for is how to send getwalletinfo to a certain wallet loaded into Bitcoin Core. The way to do this is to use that wallet's API endpoint. The endpoint is /wallet/&lt;name&gt; where &lt;name&gt; is the name of the wallet you are trying to send commands to.

So the full URL that you need to send your RPC requests to is http://&lt;ip&gt;:&lt;port&gt;/wallet/&lt;name&gt; where &lt;ip&gt; is the IP address that Bitcoin Core is listening on (probably 127.0.0.1), &lt;port&gt; is the port the RPC interface is bound to (probably 8333), and &lt;name&gt; is the name of the wallet.