I’ve heard some people saying that local storage would replace cookies in a couple of years.
That statement sound a bit false to me for one reason:
With PHP (or any server side language), we can access cookies, but I’ve not yet found anyway to access LocalStorage.
Using Ajax is not a solution:
Ajax is not a good solution as it mean I must display a page before having access to the Local Storage. In many case, that’s unacceptable. Think of storing the display language of a site, you would have to display a page once in a random(default) language, and then the site would switch for the second page.
Should we consider local storage for and only for client-side data, without any incidence on the server side ( database, etc.. ) ?
Yes, as its name implies, LocalStorage is aimed at storing data locally, at the client. It fills a different role than cookies.
You can store much more data in it, but that data isn’t sent to the server (it would be horrible to send 1Mb of data with each connection)