[kh99]

Unfortunately, the datamanager errors are designed to be displayed and not checked via a program, so the only thing you could really do is check each string in the error array against what you know the error message should be (or else just display all the error strings instead of trying to sort it out).

You could call $newuser->set('username', $username) then check $newuser->errors[] for an error, but there are actually a number of error sthat can happen from setting a name so you don't know for sure that it's "name already in use". (See includes/class_dm_user.php, function verify_username() around line 377).