[php] form id instead of name in processing

I’m no PHP expert. Actually I’m fairly new to it. I downloaded a free script for sending form data to an email address and am modifying it for my site. The trouble is, my site is valid XHTML strict, and this PHP form mailer script grabs the “name” of the <input>, when I need it to grab the “id” of the <input> instead, because name is not valid in XHTML so ids are used instead. e.g.

<input id=“message”></input>
Instead of: <input name=“message”></input>

Does anyone know how I can get PHP to grab the ids of the inputs? Thanks!