Ok, typed up something to hopefully get you started. The rar-archive (unpach with winzip, winrar, 7zip, etc.) contains:
..a VB project that accepts a connection from a client (php script) and passes the data directly to a serial connection. You need to set the correct COM-port in the source-code.
..a couple of php files that sends data to the VB backend (and thus to a COM port)
..a file called scetch.txt that I just threw together that should check if it has recieved more than 2 bytes. If it has, it treats the first as the pin-number, and the second as ON/OFF (1 = ON, whatever else = OFF)
This might not be the smoothest way to do things, but I hope it will at least get you started. If you have any questions (which I am sure you will have, trying to understand my code, heh..), feel free to ask! 
Oh, almost forgot the link! -_-'