Thanks, with safe_mode off, exec work ok, but what happen with system('id') ?
<?php
echo "Output of the 'whoami' command:<br /><br />\n";
echo exec('/usr/bin/whoami');
echo '<br/>';
system('id');
$f = fopen ("test.txt", "a");
fputs($f, "it's working !");
fclose($f);
phpinfo()...