PHP Codeigniter Directory Structure Best Practices

Here are some best practices to follow when structuring your PHP CodeIgniter project:

1. Use the Default Structure: Just like any other framework, CodeIgniter provides a default directory structure that's designed to help you organise your project efficiently. Stick to this structure as it follows industry standards and makes it easier for other developers familiar with CodeIgniter to understand your project.

2. Division of Code by Type:
   - All pieces of code are meant to perform different functions in a project and as such, they should be placed in their relevant place so everyone knows how to access any part of the codebase.
   - Models: Models are meant to be used for database-related operations and hence all queries should be driven from models.
   - Controllers: Controllers are the bridge connecting the data and the views. Hence, all exchange between the database (i.e. models) and views should be done using Controllers.
   - Views: Views are supposed to be the dumbest part of the application in the sense that there should be absolutely no logic placed in them. They should just render whatever data the controller gives them.
   - Libraries & Helpers: Code duplication is a sin and must be avoided at all cost. Create custom libraries and helpers for all functions/logical operations you need to perform in the code.
   - Constants: In any project there are global constants that we use across the project, all such constants should be placed in the "constants.php" file in the config directory.

3. Modules or Features: Organise models, controllers, views and libraries by modules. For example, all models related to the user module should be kept in one folder whereas all models related to the subscriptions module should be kept in another folder, etc.

4. Autoloading: CodeIgniter supports autoloading, which can be very helpful in managing class dependencies. If you know there are certain libraries that are going to be used across the application in multiple places, you can utilise this feature to avoid manually including files in each class.

5. Configuration Files: Keep configuration files (database, routes, etc.) separate from your code. Use the config directory for these files. A very bad practice is to hardcode config variables in models and controllers, avoid this at all costs.

6. Assets (CSS, JavaScript, Images): Create a directory for your assets, such as assets, and subdivide it further by type (css, js, images). Keep all necessary assets for the project in this directory and nowhere else.

7. Routes: Define your custom routes in the config/routes.php file. Keep the routes organised by module and make sure there are ample comments in the file for better understanding.

8. Error Handling and Logging: Set up proper error handling and logging mechanisms. As a rule of thumb, error display should be turned off on production but error logging should never be disabled. The default logs directory that CodeIgniter provides is sufficient to achieve this.

9. Localisation and Language Files: Most applications these days are supporting multiple languages i.e. internationalisation, to easily show different strings based on the preferred language of the user, organise language files in the language directory.

10. Namespaces: If you're using PHP namespaces, follow a consistent naming convention and directory structure that mirrors the namespaces. For example, if you are creating a model for managing the users module under the directory models/Users then its better to call it UsersModel.php than UserModel.php or User.php etc.

11. Documentation: It's very important to have a simple documentation file such as a `README.md` to explain the purpose of different directories, how to set up the project on local, and any specific guidelines to deploy and get the project running on a server.

12. Version Control: Always use a version control system like Git to manage your project. Make sure to include a `.gitignore` file to exclude unnecessary files from version control. As a rule of thumb, all user generated content like uploaded files etc. should be placed in gitignore as well as all external dependencies (node_modules, vendor, etc.) that we can easily download with package managers should be excluded from the git repo as well.

 

Remember, the key is to maintain consistency and make it easy for yourself and other developers to understand the structure of your project. As your project evolves, periodically review and refactor your file structure to ensure it remains organised and scalable. Also, spend some time every month to clean up unnecessary code, files and assets from the project so the technical debt never gets overwhelming as the project grows.