Thank you so much for that, that's worked a treat. I've now added the following three to the body onload in this order...
Selected in list parent (dropdown1) to <?php echo((isset($_GET["parent"]))?$_GET["parent"]:"") ?>
Populated List from Array - Source: level2 - Source List: parent - Target List: child
Selected in list child (dropdown2) to <?php echo((isset($_GET["child"]))?$_GET["child"]:"") ?>
This has now sparked off a couple of other similar issues...
The list of search results which appears simply displays the level3 names and beside each name is a link to an 'update record' page where the client can change the details of this record and then return to the original page which has the search and search results. When I make an update and return to the page, it still displays the correct search results but it hasn't retained the chosen options in either of the dropdowns. Would it require me to pass some kind server variable through to the 'update record' page and then back through to the search results page?
Secondly, the list of search results can be reordered - I've implemented the Table Drag and Drop JQuery plugin to achieve this - so the client can drag one of the results in the list up or down within the list and then clicks an 'Update Order' button. This runs a php page and reloads the search/search results page. I've tried applying the same three behaviours to the onClick of this button, but the 2 dropdowns have lost their selected options when the page reloads.
Any advice you can offer would be greatly appreciated and thank you again for your initial resolution.