CI4 add value to post array

First of all, you do not need to use superglobals in your code.
It is considered a bad practice, and you should not do it.

But if you really want to use $_POST, you could use it and it works in CI4.

PHP Code:

<?php
namespace App\Controllers;
class Home extends BaseController
{
    public function index()
    {
        $_POST['keyValue'] = 'value';
        var_dump($_POST); // You will see 'keyValue' => 'value'
    }
} 


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