Simple RSVP form validation through JavaScript, jQuery or PHP?

I am developing what I thought was a very simple RSVP form for a wedding website on Wordpress. Data will be transferred to the site administrator through email, so no need to mess with a database.

I've used these tutorials for validating/sanitizing input using PHP. As a newbie, they've both left me stumped.

http://ift.tt/18hRzJa http://ift.tt/18hRCof

I'm starting to wonder if there's an easier way, e.g., through JavaScript. If so, I was wondering about the benefits of using PHP over JavaScript and vice versa for form validation.