How to change data of reference passed Array in Closure - php

Question

I have an Eventbus that takes a filter name as its first parameter and a Closure as second parameter. Like this:
$this->EventBus->subscribe('FilterTestEvent', function(){/*Do Something*/});
It's called like this:
$filteredValue = $this->EventBus->filter('FilterTestEvent', $anyValue);
What I want now is to pass an array as reference to the Closure that then is changed in any way (here: add elements) and then return something as the filtered value:
$item_to_change = array('e1' => 'v1', 'e2' => 'v2');
$this->EventBus->subscribe('FilterTestEvent', function(&$item){
$item['new'] = 'LoremIpsum';
return true;
});
$filtered = $this->EventBus->filter('FilterTestEvent', $item_to_change);
Now I would a print_r($item_to_change) expect to look like the following:
Array
(
[e1] => v1
[e2] => v2
[new] => LoremIpsum
)
But instead it looks like the original array:
Array
(
[e1] => v1
[e2] => v2
)
The eventbus internally stores all closures and calls them if needed through call_user_func_array() with the closure as first argument and the value as the only argument array element.
How can I achieve what it's meant to do?
Source Code to the Eventbus: http://goo.gl/LAAO7B

Answer 1

Probably this line:
$filtered = $this->EventBus->filter('FilterTestEvent', $item_to_change);
is supposed to return a new filtered array, not modify the original one.
So check it:
print_r($filtered);
Passing by reference is possible by modifying a function (adding &):
function filter(&$array){ //Note & mark
$array['new_index'] = "Something new" ;
}
$array = array("a"=> "a");
filter($array); //The function now receives the array by reference, not by value.
var_dump($array); //The array should be modified.
Edit:
Make your callback return the filtered array:
$this->EventBus->subscribe('FilterTestEvent', function(&$item){
$item['new'] = 'LoremIpsum';
return $item ;
});
Passing by reference should not work here, because in the source code that $value variable is swapped with another value and returned after.

Answer 2

Ok. I found the answer. The filter function needs to be changed so that it accepts arrays as value, in which I can save the reference. For details see difference Revision 1 and Revision 2 of the Eventbus source code, here: goo.gl/GBocgl