Limit payment module to certain group of customers?

[DrByte]

Furthermore I have two general questions regarding module modification:

• If the PHP code of some module is changed, are the effects immediate?
  Or should I unpublish (remove) the module and republish (install) it before any changes will work?
• How can you debug the modules?
  Using echo / print_r commands won't work:
  there will be no screen output from within the class/method.

1. With this particular change, the effects are immediate.
2. Sometimes you need to use die() statements instead of echo/print statements, due to page-refresh actions, etc. You could also log info to a file using the errorlog() function ie: in conjunction with this contrib: http://www.zen-cart.com/index.php?ma...roducts_id=860