Copying one array to the end of another array
Be aware that sizeof is actually an operator, not a function.  It also returns std::size_t, which is an unsigned integer type.  You currently have size as an int, which is a signed type.  If you had your compiler warnings up high (and they should be), then you probably would've been warned about this.

std::size_t size = sizeof(fromArray)/sizeof(fromArray[0]);