PHP Interfaces - Define Structure Without Implementation

PHP Interfaces – Define Structure Without Implementation 🚀

An interface in PHP defines a blueprint for classes without providing implementation. It ensures that all classes following the interface have the required methods.

Interfaces are defined using the interface keyword and implemented using implements.

🔹 Why Use Interfaces?

Forces classes to follow a structure.
Allows multiple class implementations (unlike inheritance which allows only one parent).
Promotes cleaner and modular code.

📝 Example 1: Defining & Implementing an Interface

Here, we create an interface Animal with a required method makeSound(). Any class implementing this interface must define the method.

<?php
// Defining an interface
interface Animal {
    public function makeSound();
}

// Implementing the interface in classes
class Dog implements Animal {
    public function makeSound() {
        return "Woof! Woof! 🐶";
    }
}

class Cat implements Animal {
    public function makeSound() {
        return "Meow! 🐱";
    }
}

// Using the classes
$dog = new Dog();
$cat = new Cat();

echo $dog->makeSound(); // Output: Woof! Woof!
echo "<br>";
echo $cat->makeSound(); // Output: Meow!
?>

Try It Now

Both Dog and Cat classes implement the Animal interface and define the makeSound() method.

🔹 Multiple Interfaces

A class can implement multiple interfaces, allowing flexibility.

📝 Example 2: Implementing Multiple Interfaces

<?php
// Defining multiple interfaces
interface Flyable {
    public function fly();
}

interface Speakable {
    public function speak();
}

// Implementing both interfaces
class Parrot implements Flyable, Speakable {
    public function fly() {
        return "Flapping wings... 🦜";
    }

    public function speak() {
        return "Hello! Polly wants a cracker! 🦜";
    }
}

$parrot = new Parrot();
echo $parrot->fly(); // ✅ Implements Flyable
echo "<br>";
echo $parrot->speak(); // ✅ Implements Speakable
?>

Try It Now

Here, the Parrot class implements both Flyable and Speakable interfaces.

🔹 Using Interfaces for Type Hinting

Interfaces help enforce method usage when passing objects as arguments.

📝 Example 3: Interface for Type Hinting

<?php
interface Logger {
    public function log($message);
}

class FileLogger implements Logger {
    public function log($message) {
        return "Logging to file: " . $message;
    }
}

class DatabaseLogger implements Logger {
    public function log($message) {
        return "Logging to database: " . $message;
    }
}

// Function with interface type hinting
function sendLog(Logger $logger, $message) {
    return $logger->log($message);
}

$fileLogger = new FileLogger();
$dbLogger = new DatabaseLogger();

echo sendLog($fileLogger, "File system issue.");
echo "<br>";
echo sendLog($dbLogger, "Database connection lost.");
?>

Try It Now

The sendLog() function accepts any object that implements the Logger interface.

🎯 Key Takeaways

interface → Defines required methods without implementation.
Classes must implement all methods in an interface.
Classes can implement multiple interfaces.
Interfaces allow for better organization and maintainability.

📝 Practice Time!

Create an interface Driveable with a method drive(). Then, make Car and Bike classes implement it. 🚗🏍️