How to Pass Variables Into PHP Ajax Handler Script?

I have a small ajax php application, which outputs data from a mysql db into a table. The rows are links, which when clicked will call an ajax function, which in turn will call another php file, which displays a different query from the same database in a layer without reloading the page.

I would like to know how to synchronize queries between both php files. So when I click on a row in the base page, the layer will be expanded to include additional information, or indeed the whole query.

I was thinking I could do this by having the primary key in the first query for the table, however I don't want it displayed and was wondering if there was a better approach to this?

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