[zokemon]

You also should make the setValue() function public in order for other npcs to be able to call it.

EDIT:

Here is probably what you are looking for:


NPC 1

PHP Code:

function onCreated() {
  core = this;
}

public function setValue(oldVal, newVal)
(@ oldVal) = newVal; 


NPC 2

PHP Code:

function onCreated() {
  this.on = true;
  core.setValue("this.on", (this.on = !this.on));
  echo(this.on);
} 


I know I changed it quiet a bit but it is sort of hard to see exactly what you want, sorry.

SECOND EDIT:

On second thought, that won't work either as "this.on" will be using the first NPC as "this" (in essence it would be the same as doing "core.setValue("core.on", (this.on = !this.on));")