To avoid many if-else structures, let JavaScript do the trick automatically:
<select name="name" id="name">
<option value="a">a</option>
<option value="b">b</option>
</select>
<script type="text/javascript">
document.getElementById('name').value = "<?php echo $_GET['name'];?>";
</script>
<select name="location" id="location">
<option value="x">x</option>
<option value="y">y</option>
</select>
<script type="text/javascript">
document.getElementById('location').value = "<?php echo $_GET['location'];?>";
</script>