Question

Data is loaded into div #container. “itens.php” is used for any access, but each client has own database. When “itens.php” is running it already have connection to the correct client database. I don’t know the best way to use data.php (unique file, not one for each client) connect to client database.

The only manner I see is posting string with the database name, but don’t sounds good.

How good way to make that?

Itens.php:
    $(...).click(funtction(){
        (...)
        $("#container").load('data.php?id=' + id);
        (...)
    });

Answer 1

How about use a additional database to store the mapping of username to database name?

So you only need to post the username.