CodeIgniter 4 data submission returning page 404

Question

I've just started using CodeIgniter 4 and it's very different from CI 3. When doing the form submission, either by using PHP post or ajax post request, both are returning page 404.

$('#formData').on('submit', function(e){
    e.preventDefault();
    var FormData = $(this).serialize();

    $.ajax({
        type: 'post',
        dataType:'json',
        url: '<?= base_url("/send-email") ?>',
        data: FormData,
        success: function(res){
            console.log(res)
        }
    })
})

<form id="formData" method="post">
    <div class="form-group row">
        <div class="col-md-6 mb-4 mb-lg-0">
        <input
            type="text"
            class="form-control"
            placeholder="First name"
            name="firstname"
        />
        </div>
        <div class="col-md-6">
        <input
            type="text"
            class="form-control"
            placeholder="Last name"
            name="lastname"
        />
        </div>
    </div>
    <div class="form-group row">
        <div class="col-md-6 mr-auto">
            <input type="submit" id="send_email" class="btn btn-block btn-primary text-white py-3 px-5" value="Send Message">
        </div>
    </div>
</form>

PHP Code

<?php namespace App\Controllers;

use CodeIgniter\Controller;

class DefaultController extends BaseController
{
    public function send_email(){
        if($this->request->isAJAX){
            print_r($_POST);
        }
    }
}

I have form helper loaded from BaseController. I wonder if there is any other setting that need to be configured to make it work. I totally don't have any idea why.

Answer 1

Okay I have figured out the cause of the error. In order to send any request, I have to specify it in the routes of the specific method that I want to use first. In my case, I am trying to send a post request. So my routing should be like this :

$routes->post('/send-email', 'DefaultController::send_email');

Base on the doc https://codeigniter.com/user_guide/incoming/routing.html#using-http-verbs-in-routes