I'd like to know how I can do (I don't know a lot about php) in order to make all the users fitting with the ones of my website.
I mean, the users already haver to register and to log in order to come to my website, and I don't want them to have to do it again on phpwebgallerie. The point is that I could simply delete the identifying part on webgallery but I would loose a lot of options...
You can do it but it takes some work.
Take the user id and password that you have. Put them into an array and serialize the array. Then encrypt the array (security), base64_enclode the encrypted value, and attach it to a link. Reverse the process in 'identification.php'.
As I said, a little hairy, but it works.