gmap location

[Chompy]

Is there an variable saying what gmap you are on, or a function to check what gmap you are on?

for example

PHP Code:

if (isonGmap("overworld"))
  seteffect(0, 0, 0, 0.1);
else
  if (isonGmap("cave"))
    seteffect(0, 0, 0, 0.5); 


Is there a function or variable which can help me do this?