Username whitelist submit form

[moviemastersdk]

I have a website set up for a minecraft server that i'm hosting,

and i have a php page with a signup form for the server whitelist, where people fill in their
Name:
Age:
Email:
Country:
Minecraft Username:

on the site i also have a phpbb forum set up with mysql database,

the thing i would to know, is that if it's possible to check if the email and/or username is registered on the forums, and then tell them to register on the forums before signing up for the whitelist,(If there is no match)

Short. Version

User types in his credentials

Clicks submit

Server checks if the username I registered on the phpbb forum

If the username is found
He gets a you are now white listed message

If username not found
He gets a please register on the forums. Message

End



Thx in advance