Execute a shell command from php

To execute a shell command from php, typically do the following;

            <?php
            $output = shell_exec('sudo -u root monit summary');
            echo "<pre>$output</pre>";
            ?>

In the above scenario, we want to run something as root, so we need to modify our /etc/sudoers file;

Firstly, assuming the user is www-data then we can add the following line to /etc/sudoers

www-data ALL = NOPASSWD: /usr/sbin/monit

where /usr/sbin/monit is the command that we wish to allow the user www-data to run without the need to enter a password.