Extension:Extension directory

1. Extension:Extension directory

The `Extension:Extension directory` is a crucial component of any MediaWiki installation intending to leverage the vast ecosystem of extensions available to enhance its functionality. This article provides a comprehensive guide for beginners on understanding, configuring, and managing the extension directory within MediaWiki 1.40. It will cover the directory’s purpose, structure, common issues, security considerations, and best practices. We will also touch upon how this directory interacts with the Manual:Configuration settings and the Manual:Updating extensions process.

== What is the Extension Directory?

At its core, the extension directory is the location on your server where MediaWiki looks for installed extensions. Think of it as the app store for your wiki. Extensions are pre-packaged sets of PHP code, often with associated JavaScript, CSS, and image files, designed to add specific features to your wiki. These features can range from simple things like adding a table of contents generator to complex functionalities like integrating with external databases or implementing advanced Manual:Search capabilities.

Without a properly configured extension directory, MediaWiki cannot locate and load these extensions, rendering them unusable. The default location is typically `extensions/` within your MediaWiki installation directory. However, this can be customized, as we will discuss later. Understanding the directory is fundamental to extending your wiki’s capabilities beyond its basic functionality.

== Directory Structure and Files

The `extensions/` directory isn't just a dumping ground for extension files. It follows a specific structure to ensure MediaWiki can correctly identify and load extensions. Each extension typically resides in its own subdirectory within `extensions/`.

Here’s a typical example:

``` extensions/ ├── ExampleExtension/ │ ├── ExampleExtension.php │ ├── ExampleExtension.body.php (optional) │ ├── ExampleExtension.toc.php (optional) │ ├── languages/ │ │ └── English.php │ ├── images/ │ │ └── ExampleImage.png │ ├── js/ │ │ └── ExampleScript.js │ └── css/ │ └── ExampleStyle.css ```

Let's break down the key components:

• **`ExampleExtension/`**: This is the directory for a specific extension, named after the extension itself. The name is important, as it's used internally by MediaWiki.
• **`ExampleExtension.php`**: This is the *main extension file*. It's the entry point for the extension and contains the core PHP code that registers the extension with MediaWiki. This file *must* exist for an extension to be recognized.
• **`ExampleExtension.body.php`**: This optional file contains code that is executed *after* the main extension file. It can be used for tasks like registering special pages or hooks.
• **`ExampleExtension.toc.php`**: This optional file is used to generate a table of contents for the extension’s documentation page within the wiki.
• **`languages/`**: This directory contains language files that provide translations for the extension’s messages. Each language file is named after the language code (e.g., `English.php`, `French.php`). Proper language support is crucial for internationalization.
• **`images/`**: This directory stores any images used by the extension.
• **`js/`**: This directory contains JavaScript files used by the extension. These files typically handle client-side functionality.
• **`css/`**: This directory contains CSS files used by the extension to style its elements.

Not all extensions will have all of these files. Some extensions may only consist of a single PHP file, while others may have a more complex structure. However, this example illustrates the typical organization.

== Configuring the Extension Directory in `LocalSettings.php`

MediaWiki needs to know where to find the extension directory. This is configured in your `LocalSettings.php` file. The following line is usually present (and should be uncommented if not):

```php require_once("$IP/extensions/ExtensionHooks.php"); ```

This line tells MediaWiki to load the `ExtensionHooks.php` file, which is responsible for discovering and loading installed extensions.

If you've moved the `extensions/` directory to a different location, you need to update this line to reflect the new path. For example, if you've moved it to `/var/www/wiki_extensions/`, you would change the line to:

```php require_once("/var/www/wiki_extensions/ExtensionHooks.php"); ```

• • Important:** Ensure the path is correct and that the web server has read access to the directory. Incorrect paths will prevent extensions from loading and can cause errors. Always back up your `LocalSettings.php` file before making any changes.

== Installing Extensions

Installing an extension is typically a straightforward process:

1. **Download the Extension:** Download the extension package from the Manual:Extension sources (typically the MediaWiki Extensions repository: [1]). Extensions are usually distributed as ZIP or tar.gz archives. 2. **Extract the Archive:** Extract the contents of the archive into the `extensions/` directory. This will create a new subdirectory for the extension. 3. **Configure in `LocalSettings.php`:** Add the extension to the `$wgExtensions` array in your `LocalSettings.php` file. For example, to install an extension named "ExampleExtension", you would add the following line:

  ```php
  $wgExtensions[] = 'ExampleExtension';
  ```

4. **Run `update.php`:** Navigate to your wiki’s `update.php` script in your web browser (e.g., `http://yourwiki.com/w/index.php?title=Special:Update`). This script will detect the new extension and perform any necessary database updates or configuration changes. This step is *crucial*.

5. **Verify Installation:** After running `update.php`, check to see if the extension is working as expected. This may involve visiting a special page, checking for new features in the wiki interface, or examining the wiki’s configuration.

== Common Issues and Troubleshooting

Several issues can arise when working with the extension directory:

• **Extension Not Loading:** This is the most common problem. Check the following:

   *  Is the `$wgExtensions` array in `LocalSettings.php` correctly configured?
   *  Is the extension directory path in `LocalSettings.php` correct?
   *  Does the extension have a valid `*.php` file in its directory?
   *  Does the web server have read access to the `extensions/` directory and its contents?
   *  Check the MediaWiki error logs for more detailed information.  These logs are typically located in the `errors/` directory within your MediaWiki installation.

• **Permissions Issues:** The web server user needs read access to the `extensions/` directory and all files within it. Incorrect permissions can prevent MediaWiki from loading extensions. Use `chmod` and `chown` commands (on Linux/Unix systems) to adjust permissions as necessary.
• **Conflicts Between Extensions:** Sometimes, two or more extensions may conflict with each other, causing errors or unexpected behavior. Try disabling one of the extensions to see if the problem resolves. Read the documentation for each extension to identify potential conflicts.
• **Database Errors:** Some extensions require database schema changes. If these changes fail, you may encounter database errors. Check the MediaWiki error logs for details and ensure your database user has the necessary privileges.
• **PHP Errors:** Incorrectly written PHP code in an extension can cause PHP errors. Check the MediaWiki error logs for PHP error messages and contact the extension developer for assistance.
• **Caching Issues:** Sometimes, MediaWiki’s caching mechanisms can prevent changes to extensions from being reflected immediately. Try clearing the MediaWiki cache by deleting the files in the `cache/` directory (be careful, this can temporarily slow down your wiki).

== Security Considerations

The extension directory is a potential security vulnerability. Installing extensions from untrusted sources can introduce malicious code into your wiki. Here are some security best practices:

• **Only Install Extensions from Trusted Sources:** The official MediaWiki Extensions repository ([2]) is the most reliable source.
• **Review Extension Code:** Before installing an extension, review its code to ensure it doesn’t contain any malicious code. This is especially important for extensions from less well-known sources.
• **Keep Extensions Updated:** Extension developers often release updates to fix security vulnerabilities. Regularly update your extensions to the latest versions. Utilize the Manual:Updating extensions process.
• **Limit Permissions:** Ensure the web server user has only the necessary permissions to access the `extensions/` directory. Avoid granting excessive permissions.
• **Regular Security Audits:** Conduct regular security audits of your wiki to identify and address any potential vulnerabilities.

== Best Practices

• **Documentation:** Always read the documentation for each extension before installing it. The documentation will provide information on how to configure and use the extension.
• **Backup:** Back up your `LocalSettings.php` file and your wiki database before installing or updating any extensions. This will allow you to restore your wiki to a working state if something goes wrong.
• **Testing:** Test extensions in a development environment before deploying them to a production environment. This will help you identify and resolve any issues before they affect your users.
• **Version Control:** Use a version control system (like Git) to track changes to your `LocalSettings.php` file and your extensions. This will make it easier to roll back changes if necessary.
• **Organization:** Keep your `extensions/` directory organized. Use meaningful names for extension subdirectories and keep the directory clean.
• **Monitoring:** Monitor your wiki for errors and performance issues after installing or updating extensions.

== Advanced Topics

• **Customizing Extension Paths:** While the default `extensions/` directory is usually sufficient, you can customize the extension search path using the `$wgExtensionPaths` array in `LocalSettings.php`. This allows you to store extensions in multiple locations.
• **Extension Hooks:** Extensions use hooks to integrate with MediaWiki’s core functionality. Understanding how hooks work is essential for developing custom extensions or modifying existing ones. See Manual:Hooks for more information.
• **Extension Registration:** The `wfExtensionRegister()` function in the main extension file (`*.php`) is used to register the extension with MediaWiki. This function takes various parameters that control how the extension is loaded and initialized.
• **Using Composer:** Modern MediaWiki installations increasingly utilize Manual:Composer for managing extensions. Composer simplifies the installation and updating of extensions and their dependencies.

The `Extension:Extension directory` is a cornerstone of a flexible and powerful MediaWiki installation. By understanding its structure, configuration, and security considerations, you can effectively leverage the extensive ecosystem of extensions to tailor your wiki to your specific needs. Remember to prioritize security, follow best practices, and consult the documentation for each extension you install.

Manual:Configuration settings Manual:Updating extensions Manual:Extension sources Manual:Hooks Manual:Composer Special:ListInstalledExtensions Manual:Skinning Manual:API Manual:Template system Manual:Categories Special:Search

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