How would I insert something into a array in php from a button press

Question

So I have this whitelist system for my application. I want it to be able to whitelist you froma button press on my website.

The array looks like this:

$database = array(
    array(
        "key" => "Hello World",
        "hwid" => "Don't worry about it"
    )
);

I don't know if you would use something like mysql or if it is possible with javascript. Anyways thanks!