AJAX passing secret variable to php -

i have script counts number of clicks done on specific part of map. every 10 seconds through ajax send these numbers php page insert them in database.

every 10 seconds specific cell of map can clicked 1 time.

the problem if client modifies script reducing number of seconds of ajax request, can potentially infinite number of clicks.

so need pass .php secret variable cannot modified client, , .php checking if same secret variable has done in less 10 seconds insert. possible, considering fact session id , cookie can potentially modified client??