'function XxXxXx(event, player)'
event and player values are I guess sent by the core when that specific event is triggered and if this function is hooked to it then it will receive those values in a specific order.
.. i hope I got that description right lol
as far as null'n the chat back see the edited above script again.
I added a 'return false;' to the 'if' statement end to null out anything that cant be passed on but be cautious as reurn false can also cause havoc but if implemented right they can make things pro looking.