PHP exec() shell_exec() Help

Hello,

I have a audio test command

speaker-test -c 2 -t wav | sleep 5

and it works fine when i type this in the linux shell window.

BUT

when i want to run this command using php


<?php
shell_exec("sudo -u usman speaker-test -c 2 -t wav | sleep 5");
?>

It dont work and as i see the apache log i get this error message

sudo: no tty present and no askpass program specified

Then i Google and someone told to make the sudouser (in my case usman) a passwordless user.

What changes i have made in my /etc/sudoers files are

#Defaults requiretty
usman ALL=(ALL) NOPASSWD: ALL

I am really not sure how to get it working.

Kindly help.

Thank you

usmangt