My b2evolution Version: Not Entered

Hello!

I want all my posts to show the author in the bottom, but not the userID.
I want the full name + lastname shown.

For showing only the userID i use this code:

$Item->author( array(
      'before'       => T_('Av '),
      'after'        => ' ',
    ) );

How do I do this? I think I will need 2 examples of the code above, one for the Name and one for the Lastname, but what should I change "author" to?