When should type hints in PHP classes be used, and what are the advantages of using interfaces over classes as type hints?

Type hints in PHP classes should be used when you want to enforce the type of input parameters in methods or return types in functions. Using interfaces as type hints over classes allows for more flexibility and polymorphism in your code, as classes can implement multiple interfaces but can only extend one class. 

interface Logger {
    public function log(string $message);
}

class FileLogger implements Logger {
    public function log(string $message) {
        // Log message to a file
    }
}

class UserManager {
    public function __construct(private Logger $logger) {}

    public function registerUser(string $username) {
        // Register user logic
        $this->logger->log("User $username registered.");
    }
}

$fileLogger = new FileLogger();
$userManager = new UserManager($fileLogger);
$userManager->registerUser("JohnDoe");

Keywords

type hints PHP classes interfaces advantages error types

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