I believe you have to invoke the callback like so:
PHP Code:
public void Save(ActionCallback callback) {
float test[2];
test[0] = 2.0;
test[1] = 1.0;
Call_StartFunction(INVALID_HANDLE, callback);
Call_PushArray(test, sizeof(test));
Call_Finish();
}
INVALID_HANDLE indicates the callback is in the current plugin.