That's the best approach, Kobaltic. This is how virtually every language communicates with PHP I imagine--the client passes in data via GET/POST and then PHP parses the input to execute whatever functions it needs.
httpRequestASync will call the request in the background (asynchronously) so it does not lock up the rest of the app while the request is pending. This makes it possible to submit scores to a server, retrieve high scores, and so on without causing any noticeable delay to the user who can continue playing the game as this happens.
Checking for when the async call is complete is pretty straightforward using GetHTTPResponseReady(). What I do is set a variable (e.g., HTTPRequestPending) to 1 when the async request is called, and then do the following in the main loop (assuming that the HTTP connection is named HTTPConnection).
If HTTPRequestPending = 1
If GetHTTPResponseReady(HTTPConnection) = 1
// If the response includes data, you can store it
data$ = GetHTTPResponse(HTTPConnection))
// Close HTTP Connection
HTTPRequestPending = 0
CloseHTTPConnection(HTTPConnection)
DeleteHTTPConnection(HTTPConnection)
Endif
Endif