Facebook PHP SDK: Get user's username or ID

I'm working on app, that should work like this:

• After logging in, you can enter another user's profile URL (or something else?) who can then enter the page and see the note you left there for him


• Another user logs in, app checks if it is the right one (by url?) and then lets him access the page and see your note

I wanted to use IDs, but that doesn't work because FB won't give you ID of someone else before he uses your app. URLs were a good idea, but then it crashed because GraphAPI doesn't provide user's url anymore (deprecated). I don't want to let the people 'register' first by logging in and then wait for the note from another user.. That is not the surprise anymore.

Do you have any idea how could I do this ? Thank you.

It used to be pretty simple with v1.0 of GraphAPI :( If there is no solution for it, I will use the 1.0 and close the app on April.