Serial problems

In my job to become "MICROSOFT" free, i have a computer with a termical serial printer.
Ubuntu 8.10 LAMP, and the PHP lines:

`mode COM1: BAUD=19200 PARITY=N data=8 stop=1 xon=off`;

$sp = fopen("COM1", "w+");

gives me the error:

Warning: fopen(COM1) [function.fopen]: failed to open stream: Permission denied in /var/www/a.php

Have tryed every tips on the net.
chmod a+rw /dev/ttyS0 did not work.

HELP......