Hallo Danius,
<select name="search_for">
<option value="name" >Name</option>
<option value="tel_search" >Telefonnummer</option>
<option value="knowhow_search" >KnowHow</option>
</select>
Nimm den Inhalt aus $_POST (bei PHP) z.Bsp.
<option value="tel_search"<?php if($_POST["search_for"] == "tel_search"){echo" selected";} ?>>Telefonnummer</option>
Gruß Rainer