keep track of a global value on a website

I'm currently working on a project that involves a website which gets data from a game API.

Problem is, I am bound to a specific Rate limit (of currently 500 requests per 10 minutes) which i must not exceed.

How do i keep track of the current count of requests other than writing / reading it to a file / database everytime someone requests the data (i guess that woulnd't be the best approach and could potentially ?! lead to problems with a few houndred people accessing the website at the same time)

The website calls a php script with neccessary information the user provides to get the data from the API