select

<select name="car">
  <option value="volvo">Volvo</option>
  <option value="saab">Saab</option>
  <option value="opel">Opel</option>
  <option value="audi">Audi</option>
</select>

<?php
$car = $_POST['car'];
$sqlq = "INSERT INTO table_name (column1, column2, column3,...) VALUES (value1, value2, value3,...)";
?>