how to get the username in plugincode?

[Disasterpiece]

Hi

i'm currently working on a new plugin and in the plugin's php code, i need access to the username. If the user is not logged in, the script will fall back to "guest".
Because the default username is "Unregistered" (depending on the board's language) i also need a way to check if the user is logged in or anonymous.

i know how to access the username via template code: {vb:raw bbuserinfo.username}
but i don't know how to access it in the actual plugin code.

thx in advance!