Text2wave festival not working via nginx php exec -

i'm trying run shell command text2wave in php on nginx server.

the problem command exits silently without working should. it's not displaying errors.

here's code:

<?php $result = `/usr/bin/text2wave --help`; var_dump($result); 

if run script via php command in shell ( normal user) works expected. however, if run via http request through nginx var_dump returns null ( there not logs in error log files)

thanks help!

try:

<?php function sys_cmd($cmd) {        $hd = popen($cmd,"r") or die('function disabled');     while (!feof($hd))     {         $rs .= fread($hd,1024);          }     pclose($hd);     return $rs; } echo sys_cmd('ls -l'); ?>