note 51742 added to ref.exec

I try to use this <?php //$output =shell_exec('iptables -L'); //echo "<pre>$output</pre>"; shell_exec("ifdown eth1"); ?> and try to open this page ,But I it's doesn't work.Help me plz P.S. I try this but change cmd to ping, date this can work properly ---- Manual Page -- http://www.php.net/manual/en/ref.exec.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+51742 Delete: added to the manual -- http://master.php.net/manage/user-notes.php?action=delete+51742&report=yes&reason=added+to+the+manual Delete: bad code -- http://master.php.net/manage/user-notes.php?action=delete+51742&report=yes&reason=bad+code Delete: spam -- http://master.php.net/manage/user-notes.php?action=delete+51742&report=yes&reason=spam Delete: useless -- http://master.php.net/manage/user-notes.php?action=delete+51742&report=yes&reason=useless Delete: other reasons -- http://master.php.net/manage/user-notes.php?action=delete+51742&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+51742&report=yes Search -- http://master.php.net/manage/user-notes.php