从函数中调用非全局变量？

Question

During the development of a Joomla! plugin, I ran across something really interesting. One of the events does not have a return value, but it calls variables from inside the function. Prior knowledge tells me this should only work if the variables are global inside the function, yet the dispatcher is able to call the variables from outside the function.

EDIT: I just discovered that the variable that is accessed from inside the function needs to be one of the paramaters! Could this be func_get_params() or call_user_func()?

Calling Code:

$instance = JDispatcher::getInstance();
$instance->trigger(onJoomCalledEvent, array(&$link, $other_params));

Plugin (snippet):

class plgMyPlugin extends JPlugin{

    onJoomCalledEvent($link, $other_params){
        $link = "Some Value Here";
        return false;
    }
}

This function returns false, yet somehow the application (Joomla!) is able to extract the value of $link. How is this done?

Answer 1

Does the plug-in definition look like this:

class plgMyPlugin extends JPlugin{

    onJoomCalledEvent(&$link, $other_params){
        $link = "Some Value Here";
        return false;
    }
}

Than it's pass by reference. If it's indeed the way you posted above than it's call time pass by reference which is deprecated and emits a warning starting with PHP 5.3.