php in explorer

[bunglebrown]

This code doesn't work in Internet Explorer (all others seemingly perfect) for some reason - it attempts to keep some checkboxes in the state they were submitted on the previous page.

<?php
// Tick boxes if user has ticked them
if($_POST['A1'] == 1) {
$img_A1 = "Images/chkbox_ticked.png";
}

else {
$img_A1 = "Images/chkbox_empty.png";
}

echo "$img_A1";
?>

Anyone happen to know why?