Imagine that HTML page is a game surface (see picture).
User can have n number of boards (blue divs) on his page. Each board can be moved, re-sized, relabeled, created new and removed.

Inside each board there are m number of figures (purple divs). Each of these user can move inside the board or to another board, re-size, change color and label, delete, add new.
The goal of the game is not important, but let's say it is to rearrange figures in a certain way so that they disappear.

But the goal of the programmer is to save the whole game surface in the database for every user of the site, and to load it later when he returns.

So, how do I go about data exchange between client and the database? I'll give my idea in one of the answers.