Why does routing fail?

Hi.

## overview
I'm trying to make `$ routes-> get` and` $ routes-> post` on the update screen, but the routing that receives the id doesn't work.
Especially the second post method output "` Undefined array key 0`
https://drive.google.com/file/d/1QnEnUe9...p=drivesdk

What may be the cause?
Commenting out `$ routes-> post` will display the get method successfully.

## reference
https://ci-trans-jp.gitlab.io/user_guide...uting.html

PHP Code:

$routes->get('school/certification/edit/(:num)', 'SchoolCertificationController::editGet/$1', ['as' => 'certification_edit_get']);
// TODO: For some reason I get an Undefined array key 0 when I add this
$routes->post('school/certification/edit/(:num)', 'SchoolCertificationController::editPost/$1', ['as' => 'certification_edit_post']);