Search Function PHP Code Help Please

Hey guys I cant seem to get this search form to allow a user to select between a new make and a used make. Could you tell me what im doing wrong ?
When a user uses the form it works fine, however when the user tries to switch the option from NEW to used it wont allow you to switch. Below you can find a link to a zip download that contains the search code. Could you tell me what Im doing wrong when it comes to allowing the user to switch between used and new?

<table class="search">

<tbody>

<tr class="head-tab">

<td class="field">Search</td>

<td class="value">

<ul class="search_tabs">

<li class="first active">New</li><li class="last">Used</li>

</ul>

</td>

</tr>

</tbody>

</table>

1) Is this a PHP question or an HTML question? If the latter then it needs to be put into the HTML forum.
2) Assuming it is PHP, I see no form coding for calling your PHP script.
3) There is no "link below."
4) Do not expect people here to go looking for your code. Post the code here.

See ManiaDan's New User Guide to see how to post a proper question and for many debugging tips.