[FIXED] How do I use underscores and lowercase letters in URLs in Codeigniter 3?

Issue

I am annoyed with encountering mysterious problem. My development environment has been created with the following directory structure.

document_root
　└ project
　　├ application
　　│├ controllers
　　││└ admin
　　││　├ Users.php
　　││　├ Facility_Categories.php
　　││　└ Facilities.php
　　│└ views
　　│　└ admin
　　│　　├ users
　　│　　│└ index.twig
　　│　　├ facility_categories
　　│　　│└ index.twig
　　│　　└ facilities
　　│　　　└ index.twig
　　└ public
　　　└ index.php

In the development environment, these URLs appeared as expected.

https://www.example.com/project/admin/users/
 -> load admin/Users.php index function
https://www.example.com/project/admin/facilities/
 -> load admin/Facilities.php index function
https://www.example.com/project/admin/facility_categories/
 -> load admin/Facility_Categories.php index function

Recently, when I upload these files to a test environment. URL were not displayed correctly that contained "underscore". It looks like controller is not loaded.

https://www.example.com/project/admin/users/
 -> load admin/Users.php index function
https://www.example.com/project/admin/facilities/
 -> load admin/Facilities.php index function
https://www.example.com/project/admin/facility_categories/
 -> 404 Page Not Found (display codeigniter show_404 function)

By the way, if the URL is capitalized, the controller will load but View will not. (view is also displayed if view's direcotry name is capitalized.)

https://www.example.com/project/admin/Facility_Categories/
 -> 500 Internal Server Error
      (Twig\Error\LoaderError : Unable to find template "admin/Facility_Categories/index.twig")

I want to access with lower case URL. How can I solve the problem?

Solution

I solved this problem on my own to read following url

CodeIgniter Controller Case-Sensitive

CodeIgniter3 seemed to have to capitalize only the first letter of the controller name and all lowercase after that. (OK: Facility_categories.php NG: Facility_Categories.php)

I just changed 2 points.

1. Change Controller File Name From Facility_Categories.php To Facility_categories.php
2. Change Controller Class Name From class Facility_Categories To class Facility_categories

Now I can access to url that contain lowercase and underscores

https://www.example.com/project/admin/facility_categories/

Answered By - qwe001