Begging for solutions.
Use a real operating system. Windows sucks.
The PHP serial class can not read from the serial port on Windows due to some fundamental flaw in how Windows handles the serial port stream.
I dug into exactly what the issue was, years ago, but I've forgotten exactly what the problem was. I just know that it can't be fixed given Window's handling of the serial port.
There are, of course, plenty of alternative scripting languages that use Windows-exposed APIs to deal with the serial port that can work bi-directionally on Windows.
Or, create an executable application, instead.