How to update value by Events in CodeIgniter 4 - php

Question

Here is my code:
\app\Controllers\My_controller.php
namespace App\Controllers;
use CodeIgniter\Events\Events;
class My_controller extends App_Controller {
function __construct() {
parent::__construct();
require_once(APPPATH . "update_value.php");
}
function index() {
$array = array("foo", "bar");
Events::trigger('add_value_to_array', $array);
print_r($array);
}
}
\app\update_value.php
use CodeIgniter\Events\Events;
Events::on('add_value_to_array', function($array) {
error_log("add_value_to_array" . PHP_EOL, 3, "events.txt");
array_push($array, "new");
return $array;
});
I'm getting this output:
Array ( [0] => foo [1] => bar )
But it's triggering the event because it's giving a log containing this text: add_value_to_array
I want the updated array containing the 'new' item. My expected result:
Array ( [0] => foo [1] => bar [2] => new )
Is it possible? Thanks in advance.

Answer 1

Passing by reference vs. passing by value
When you pass a parameter to a function and subsequently make changes to that parameter within the function, the PHP interpreter passes that parameter by copy, not by reference. This means that changes you make to the parameter inside the function have no effect on the original value outside of the function.
Hence why you don't see the value of $array updated outside of the Event callback. The array you're expecting to see is returned by that Event callback, but you're not capturing it.
If you need to modify $array in-place, you tell PHP to pass by reference by prefixing the parameter with an ampersand (&$array) when passing it.