<?php
$loadQuality = "hi";
if (isset($_GET["loadmode"]))
{
    if ($_GET["loadmode"] == "hi") { $loadQuality = "hi"; }
    else if ($_GET["loadmode"] == "lo") { $loadQuality = "lo"; }
    else { $loadQuality = "hi"; }
}
else
{
    $loadQuality = "hi";
}

if ($loadQuality == "hi") { /* Hi Quality */ }
else { /* Lo Quality */ }
?>

<form id="mySuperLoadForm" action="load.php?loadmode=hi" method="get">
<!-- bla bla bla -->
    <select id="mySelectId" name="mySelect">
        <option onChange="document.getElementById('mySuperLoadForm').action='load.php?loadmode=hi'" selected="selected" >Hi</option>
        <option onChange="document.getElementById('mySuperLoadForm').action='load.php?loadmode=lo'" >Lo</option>
    </select>
<!-- bla bla bla -->
    <input type="submit" value="Submit" />
</form>