How would I make a Save script to save across different games (Not places)?

I know you can save stuff and be able to load the stuff from another game if it's under the same universe, but how would I go about making a Universal Save, that lets me export stuff using a special code in one game, then Load the stuff in any other game on roblox that has the specified load script?

I know I could use http and PHP and stuff, but is there any other way? And if there isn't, how would I go about using PHP to do what I want?

I just want some sort of server where I can store string(s) that any script can view but can't edit without a special code.

How would I do this?