<?php
$oneSelect = ["opt0" =>["title" => "Первая опция", "selected" => ""],
"opt1" =>["title" => "Вторая опция", "selected" => ""],
"opt2" =>["title" => "Третья опция", "selected" => ""]
];
// в uri (...&one_select=opt1)
$oneSelect[$_GET["one_select"]]["selected"] = "selected";
?>
<select>
<?php foreach($oneSelect as $option): ?>
<option <?=$option["selected"]?>><?=$option["title"]?></option>
<option <?=$option["selected"]?>><?=$option["title"]?></option>
<?php endforeach; ?>
</select>#^([a-f\d]{6}|[a-f\d]{3})$i#