I guess its a quirk of mySQL as much as anything.
I had a look and found this sort of thing as a suggestion, e.g. adding:
<?php
if (isset($_POST["Update"])) {
if ($_POST['Date_Done_in_GIS'] != '') {
$_SESSION['Date_Done_in_GIS'] = ($_POST['Date_Done_in_GIS']);
} else {
$_SESSION['Date_Done_in_GIS'] = Null;
}
}
?>
And changing:
."" . $WA_AB_Split . "".((isset($_POST["Date_Done_in_GIS"]) && $_POST["Date_Done_in_GIS"]!="" )?date("Y-m-d H:i:s", strtotime($_POST["Date_Done_in_GIS"])):"")
to
."" . $WA_AB_Split . "".((isset($_POST["Date_Done_in_GIS"]) && $_SESSION["Date_Done_in_GIS"]!="" )?date("Y-m-d H:i:s", strtotime($_POST["Date_Done_in_GIS"])):"")
But without any luck.
If you know any tricks to force it to enter blank or NULL in the date field when the form is updated without those fields being populated that would be a great help.