【PHP】クラスとインスタンスの使い方と活用法5選

class MyClass {
    // プロパティの宣言
    public $prop1 = "I'm a class property!";

    // メソッドの宣言
    public function setProperty($newval) {
        $this->prop1 = $newval;
    }

    public function getProperty() {
        return $this->prop1 . "\n";
    }
}

class Car {
    public $color;

    public function __construct($color) {
        $this->color = $color;
    }

    public function getColor() {
        return $this->color;
    }
}

$myCar = new Car("red");
echo $myCar->getColor(); // "red"が出力されます

class Rectangle {
    public $width;
    public $height;

    public function __construct($width, $height) {
        $this->width = $width;
        $this->height = $height;
    }

    public function getArea() {
        return $this->width * $this->height;
    }
}

$myRectangle = new Rectangle(5, 10);
echo $myRectangle->getArea(); // 50が出力されます

class Vehicle {
    public $color;

    public function __construct($color) {
        $this->color = $color;
    }

    public function getColor() {
        return $this->color;
    }
}

class Car extends Vehicle {
    public $doors;

    public function __construct($color, $doors) {
        parent::__construct($color);
        $this->doors = $doors;
    }

    public function getDetails() {
        return $this->color . " color and " . $this->doors . " doors";
    }
}

$myCar = new Car("red", 4);
echo $myCar->getDetails(); // "red color and 4 doors"が出力されます

abstract class Animal {
    abstract public function makeSound();
}

interface Walkable {
    public function walk();
}

class Dog extends Animal implements Walkable {
    public function makeSound() {
        echo "Woof!\n";
    }

    public function walk() {
        echo "The dog is walking.\n";
    }
}

$myDog = new Dog();
$myDog->makeSound(); // Woof!が出力されます
$myDog->walk(); // The dog is walking.が出力されます

trait SayWorld {
    public function sayHello() {
        parent::sayHello();
        echo 'World!';
    }
}

class Base {
    public function sayHello() {
        echo 'Hello ';
    }
}

class MyHelloWorld extends Base {
    use SayWorld;
}

$o = new MyHelloWorld();
$o->sayHello(); // Hello World!が出力されます

class User {
    public $name;
    public $email;

    public function __construct($name, $email) {
        $this->name = $name;
        $this->email = $email;
    }

    public function sayHello() {
        echo "こんにちは、{$this->name}さん\n";
    }
}

$user = new User("田中", "tanaka@example.com");
echo $user->name;  // 田中
echo $user->email; // tanaka@example.com
$user->sayHello(); // こんにちは、田中さん

class Product {
    public $name;
    public $price;

    public function __construct($name, $price) {
        $this->name = $name;
        $this->price = $price;
    }
}

class Cart {
    private $items = [];

    public function addProduct(Product $product) {
        $this->items[] = $product;
    }

    public function getTotal() {
        $total = 0;
        foreach ($this->items as $item) {
            $total += $item->price;
        }
        return $total;
    }
}

$product1 = new Product("りんご", 100);
$product2 = new Product("バナナ", 200);

$cart = new Cart();
$cart->addProduct($product1);
$cart->addProduct($product2);

echo $cart->getTotal(); // 300

class Database {
    private $connection;

    public function __construct($hostname, $username, $password, $database) {
        $this->connection = new mysqli($hostname, $username, $password, $database);
        if ($this->connection->connect_error) {
            die("データベース接続エラー: " . $this->connection->connect_error);
        }
    }

    public function query($sql) {
        $result = $this->connection->query($sql);
        if ($this->connection->error) {
            die("クエリエラー: " . $this->connection->error);
        }
        return $result;
    }

    public function close() {
        $this->connection->close();
    }
}

$db = new Database('localhost', 'username', 'password', 'database');
$result = $db->query("SELECT * FROM users");
$db->close();

class CustomException extends Exception {
    public function errorMessage() {
        $errorMsg = 'エラー on line '.$this->getLine().' in '.$this->getFile()
        .': <b>'.$this->getMessage().'</b> is not a valid E-Mail address';
        return $errorMsg;
    }
}

$email = "example_at_example_dot_com";

try {
    if(filter_var($email, FILTER_VALIDATE_EMAIL) === FALSE) {
        throw new CustomException($email);
    }
} catch (CustomException $e) {
    echo $e->errorMessage();
}

class ApiRequest {
    private $baseUrl;

    public function __construct($baseUrl) {
        $this->baseUrl = $baseUrl;
    }

    public function get($endpoint) {
        $ch = curl_init($this->baseUrl . $endpoint);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        $response = curl_exec($ch);
        curl_close($ch);
        return json_decode($response);
    }
}

$apiRequest = new ApiRequest('https://example.com/api/');
$response = $apiRequest->get('users');