just if myArray[key] then .... end
example :
myArray = { myFunc = function() return "thegame" end, a = "2", 3 }
myArray.a (or [a]) exists, but not myArray[c] (or .c).
so : if myArray[c] then blblabala end
which is actually if myArray[c] ~= nil then.
edit : ok to jim, I wanst sure of what was asked