Codeigniter 3.1.8 JSON Post fails

It looks okay to me...
Make sure that file_get_contents are activated by trying it on another resource.  ->raw_input_stream utilizes that function.

PHP Code:

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Postman extends CI_Controller {
    
    public function index()
    {
        if( $this->input->is_ajax_request() )
        {
            $json = $this->input->raw_input_stream;
            $json = json_decode($json);
            /**
            $json now looks like
                stdClass Object
                (
                    [user] => 1
                )
                
            Access it like
            echo $json->user;
            **/
            
            // Process json...
            
            // Data to send back
            $data = array('success' => 'true');
            
            // Send back json
            $this->output
                    ->set_content_type('application/json')
                    ->set_output(json_encode($data));
        }
    }
} 


Postman settings:
Content-Type: application/json
X-Requested-With: xmlhttprequest