prevent multiple submissions to an anonymous survey

I was asked for an easy way to prevent multiple submissions to an anonymous survey by reloading the page; so, I created a quick PHP and add submission date and client IP. We will know if the person did multiple submissions by reloading the page. Here is the code:

This survey was complete on <?php echo date("F j, Y, g:i a"); ?> from the following IP address: <?php echo $_SERVER['REMOTE_ADDR']; ?>