Are there some examples or guides on how to post a players score to an API?

I want to send the score to my own API along with the value of a session var $_username via a POST. Are there guides on the best way to do this?

Thanks

Best way is to use for example FIREBASE API or PLAYFAB, prob more out there and free but i only use the 2.

You could do it using SQL POST & RECIEVE, not recommended however, but it depends on what security level your app/game needs.

When you say your own API, is it your own? If its not to important what API your using, but you just want to store values in a database kind of way, then i strongly recommend firebase API.