<?php
        $username = 'hello';
        $password = 'hello';
        $node = 'my ip';
        exec('sudo -S ejabberd /usr/sbin/ejabberdctl register '.$username.' '.$node.' '.$password.' 2>&1',$output,$status);
        if($output == 0)
        {
            // Success!
            echo 'success';
        }
        else
        {
            // Failure, $output has the details
            echo '<pre>';
            foreach($output as $o)
            {
                echo $o."n";
            }
            echo '</pre>';
        }
    ?>

sudo: /etc/sudoers.d is world writable
        [sudo] password for daemon: