A POS printer is (mostly) not a printer in the sense of using the Windows printing functions to create output, that is quite independent of the device, but simply a sink for serial data in the printer's control language (we built a ticketing system driving very similar printers).
One approach is to user the Win32API
extension for PHP and the OpenDriver
API, but this turns out to be quite a mess. Best way is to simply fopen()
the printer port and write your PCL data via fwrite()