How can interfaces be used in PHP programming to improve the design and functionality of classes?

Interfaces in PHP can be used to define a contract for classes, ensuring that they implement specific methods. This allows for better code organization, reusability, and flexibility in the design of classes. By implementing interfaces, classes can be easily interchanged without affecting the overall functionality of the code.

// Define an interface that specifies a method
interface LoggerInterface {
    public function log($message);
}

// Implement the interface in a class
class FileLogger implements LoggerInterface {
    public function log($message) {
        // Log message to a file
    }
}

// Implement the interface in another class
class DatabaseLogger implements LoggerInterface {
    public function log($message) {
        // Log message to a database
    }
}