Use PHP to play audio on server

I am trying to use PHP to play a sound ON SERVER SIDE once someone visits my webpage. It's running on Nginx/Php5 (raspberry pi).

This is how I'm trying to do it:

I have executed command:

sudo usermod -aG audio www-data

The php file:

<?php
$audio = shell_exec('sh play.sh');
echo $audio;
?>

But it results nothing.

Running 'id' command with the same method results:

uid=33(www-data) gid=33(www-data) groups=33(www-data),29(audio),44(video)

I don't know if its relevant but:

ls -lah /dev/snd

drwxr-xr-x   3 root root      160 Oct 26 17:22 .
drwxr-xr-x  15 root root     3.5K Oct 26 17:22 ..
drwxr-xr-x   2 root root       60 Oct 26 17:22 by-path
crw-rw----+  1 root audio 116,  0 Oct 26 17:22 controlC0
crw-rw----+  1 root audio 116, 16 Oct 26 17:22 pcmC0D0p
crw-rw----+  1 root audio 116, 17 Oct 26 17:22 pcmC0D1p
crw-rw----+  1 root audio 116,  1 Oct 26 17:22 seq
crw-rw----+  1 root audio 116, 33 Oct 26 17:22 timer

Executing the following command plays the file properly:

sudo -u www-data play ding.mp3

But using the following one:

sudo -u www-data sh play.sh

Results:

Sorry, user www-data is not allowed to execute '/usr/bin/play /var/www/ding.mp3' as www-data on raspberrypi.

The script contains the following:

#!/bin/sh
sudo -u www-data /usr/bin/play '/var/www/ding.mp3'

Any other command in that script is executed properly. Anyone could give me some advice?