What are common best practices for organizing PHP files in a directory structure?

Organizing PHP files in a directory structure helps maintain a clean and structured codebase, making it easier to navigate and manage files. A common best practice is to separate different types of files (e.g., classes, functions, configurations) into their respective directories. This can help improve code reusability, scalability, and overall maintainability.

// Example directory structure:
// - classes/
// - functions/
// - config/
// - index.php