title: Server-side validation and form action
body: <p>I have a page (call it <b>form.php</b>) with a form for users to fill out. When the form is submitted, I want to validate it with a server-side script (call it <b>validate.php</b> if necessary, although the code could also go in one of the other pages if that would be better). If any part of the form fails validation, I want to kick back to <b>form.php</b> with the fields the user needs to fix highlighted. If the form passes validation, I want to go to another page, <b>success.php</b>.</p>
  
  <p>Which page should I put in the "action" attribute of the <code>&lt;form&gt;</code> element, and what's the best way to get from that page to one of the others?</p>