Creating a PHP web page that allows you to restart the server on Linux?

Question

Creating a PHP web page that allows you to restart the server on Linux?

I want to create a web page that allows the user to initiate a reboot on the linux server. Obviously, this will be available only to system admins, and will also be controlled using iptables.

Below is an example of code that I was thinking about using, but I wanted to know if there is another way to do this and how to use it on a web page? Also, is there anything else I should consider?

$command = "cat $pass | su -c 'shutdown -r now'";
$output = array();
try{
    echo shell_exec($command);
    exec($command, $output);
    system($command, $output);
}
catch(Exception $e) {
    print "Unable to shutdown system...\n";
}

foreach ($output as $line) {
    print "$line<br>";
}