void quest::set_zone_flag(int zone_id); what to do exactly?

[Arex]

i already saw it a lot of times, but i dont know the answer to my question...perhaps i dont understand wikki perfectly because my english isnt too much good. then if u want that i can help with key quests, can anybody answer to my question? when a guy finish a access quest to one zone and he get his key to that zone, i should use quest::set_zone_flag(zone_id) for give access to that zone for that player??????

Thank You!