Dynamic form fields using php and javascript

I have read various solutions to this problem but I am having trouble getting mine to work, I thought I would give the basics of what I am trying to do and hope someone can help, I am intermediate in PHP but Javascript I'm a noob.

I am trying to create a form that filters each of the subsequent list boxes, I require the form to have 4 drop down lists (There are more fields on the form but they are not linked to the database) that must filter and populate the underlying list box.

The form fields are as follows:-

Simulation
Season
Race
Driver

The tables names and fields are as follows:-

sd_sls_t_games - IDgame, GameName
sd_sls_t_seasons - IDseasin, IDGame, SeasonName
sd_sls_t_races - IDrace, IDseason, IDtracks ----- sd_sls_t_tracks - IDtracks, TrackName
sd_sls_t_driver_cars - IDdriver, IDseason ----- sd_sls_t_driver - IDdriver, FName, LName.

I have created this SQL which brings back all the data I need:-

SELECT g.GameName
, s.SeasonName
, t.TrackName
, CONCAT(d.FName,' ',d.LName) AS DriverName
FROM sd_sls_t_games g
, sd_sls_t_seasons s
, sd_sls_t_races r
, sd_sls_t_tracks t
, sd_sls_t_driver_cars dc
, sd_sls_t_drivers d
WHERE g.IDgame = s.IDgame
AND s.IDseason = r.IDseason
AND r.IDtracks = t.IDtracks
AND r.IDseason = dc.IDseason
AND dc.IDdriver = d.IDdriver

I am really stuck as to how to break this down, any help on this would be much appreciated. I am not sure of the best way to do it, do I re-sumbit the form each time and post the result or is there a better way.

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