Here the content of my test-file called test.php

```
<?php
echo exec('ls -al');
?>

```

When I ftp this to my host and run it by calling /test.php it nicely shows the content of my directory. But when I put this file on my personal server (ubuntu 12.04) it don't show any content. I've tested more commands and they all went well on my domain but not on my personal server. So, I think it's a setting of somekind but I don't no what. Could anybody tip me what to set so I can call linux-commands from php?