Send bit to specific parallel port pins with php

I need to send a bit (pulse) to specific pins of a parallel port to control some stepper motors ...

With the php_serial.class.php class I know how to send a string, but how do I send only a bit and specifically for a port? Is it possible?

$serial->deviceSet("COM6");
$serial->confBaudRate(9600);
$serial->confStopBits(1);
$serial->confCharacterLength(8);

$serial->deviceOpen();

$serial->sendMessage("\xFF\x01\x01");

$serial->deviceClose();