shell_exec php not working why?

Question

PHP

Good afternoon!
I am trying to convert file in php script like this

$var = shell_exec('/usr/bin/sox sound.wav sound-conv.ogg -G rate 8000');
echo $var;

In the console command
/usr/bin/sox sound.wav sound-conv.ogg -G rate 8000
Works great!

If I do so

$var = shell_exec('dir');
echo $var;

It displays everything, the contents of the directory, which means that shell_exec itself works ..
I missed something somewhere, tell me what?

Answer 1

I figured it out, it was the rights to the directories