problem in silent printing using php

Question

I am doing work on php and want to do silent printing of pdf through php using network printer. I have tried:

$filepath='./pdf/offer.pdf'
$adobe_path='"C:/Program Files/Adobe/Reader 8.0/Reader/AcroRd32.exe"';
shell_exec ($adobe_path.' /t '.$filepath);

This works but it doesn't work through other system on network printer.

When I want to open note pad through shell_exec() it does not open. While some other exe work well.

What is an appropriate solution for this?