codeigniter-url-resolution

name	codeigniter-url-resolution
description	Use when: ensuring a CodeIgniter application resolves URLs correctly on local/test and production hosts.

CodeIgniter URL Resolution Skill

This skill explains how to write a CodeIgniter application so URLs resolve correctly across different hosts and environments.

Key Principles

1. Use the public folder as the web server document root.
2. Keep host-specific values out of your views and controllers.
3. Define the base URL through environment configuration.
4. Always include a trailing slash on app.baseURL.
5. Use CodeIgniter route and URL helpers instead of hard-coded links.

Recommended Configuration

app/Config/App.php

• Set a default base URL for local development.
• Override it with env('app.baseURL') so production and test hosts can provide their own value.
• Normalize it with rtrim() and add a trailing slash.

Example pattern used in this app:

public string $baseURL = 'http://localhost:8080/';

public function __construct()
{
    parent::__construct();

    $configuredBaseURL = rtrim((string) env('app.baseURL', $this->baseURL), '/');
    $this->baseURL = ($configuredBaseURL === '' ? $this->baseURL : $configuredBaseURL) . '/';
}

.env and environment variables

• Use the .env file in development and test environments.
• Use actual environment variables on production.

Example .env values:

app.baseURL = 'http://localhost:8080/'

Production example:

app.baseURL = 'https://example.com/'

If your application runs in a subdirectory:

app.baseURL = 'https://example.com/subfolder/'

Public web root and rewrite rules

• Ensure the web server points to public/ as the document root.
• If you cannot point the web root at public/, use front-controller bootstrap logic carefully.
• Use public/.htaccess to route requests to index.php and remove index.php from URLs.

If public/.htaccess is active, set:

public string $indexPage = '';

and keep uriProtocol at REQUEST_URI for normal server behavior.

URL helper usage

• Use built-in helpers like base_url() and site_url() in views and templates.
• Avoid hardcoding hostnames or protocol strings in HTML.

Example:

<a href="<?= base_url('dashboard') ?>">Dashboard</a>

Handling test vs production hosts

• Test host: local or staging servers should set app.baseURL to match their HTTP host.
• Production host: set app.baseURL to the live domain.
• Keep the same routing logic and controller code across environments.
• Use allowedHostnames if the app should accept additional hostnames besides the configured base URL.

Troubleshooting

• If pages 404, verify public is the document root and .htaccess rewrite rules are working.
• If base_url() generates the wrong host, check the app.baseURL environment setting.
• If index.php appears in URLs unexpectedly, ensure indexPage is set to an empty string and the server rewrite module is enabled.

Best practice summary

• Base URL belongs in environment configuration, not hardcoded app logic.
• Normalize the base URL with a trailing slash.
• Keep the public directory as the entry point.
• Use helpers and routes for links, not explicit hostnames.
• Support both local/test and production hosts with the same app code.