I'll try to make myself clear with an example: Imagine an admin page to add a product to a database (product list). When I open the ADD ITEM page, the item is not yet created (not until I click the submit button), but let's say I want to add categories this product will appear in (with AJAX for example). When I run the AJAX script, i need to tell it which ID (my product) to put these categories in... How should I do this.? Is inserting a blank item in the database (to get mysql_insert_id) when the page opens a good way to do this.? Is it prone to conflicts or errors..? How do you guys do it.?