Get user's email

[Penicillin]

Hello
I'm designing a php page contains 3 text boxes: (Username, Password and Email).
When a user enters his username and password correctly, output his email in Email text box.
I know I have to use global.php but I don't know how to use
Please anyone give me a clue.

Thanks

[Opserty]

If all you want to do is get the Email and nothing else, you could just fetch it directly from the database. Otherwise you can make them login (through vBulletin) and just output the email through the $vbulletin->userinfo['email'] variable.