PHP? PHP5?? ???? ?????(OOP)? ???? ??? ????? ?????. OOP? ?? ????? ???? ??? ??? ????? ????? ?? ???? ???? ????? ????. PHP?? ?? ?? ??????? ??, ??? ? ??????? ? ?? ?? ??? ????.

1. ??

???? ? ???? ?? ???? ??? ???? ???? ? ??? ?????. ??? ???? ?? ??? ?? ?? ????? ??, ??? ???? ?? ??? ?? ?? ????? ???. ?? ???? ?? ???? ??? ???? ??? ? ??? ?? ?????? ??? ? ????.

?? ?? $name ? $color ??? eat() ? sleep() ???? ?? ?? ??? Animal? ??? ? ????. ?? ?? Animal ????? ???? bark() ???? ???? Dog ??? Dog? ??? ? ????.

class Animal {
    protected $name;
    protected $color;
    
    public function eat() {
        echo "$this->name is eating.
";
    }
    
    public function sleep() {
        echo "$this->name is sleeping.
";
    }
}

class Dog extends Animal {
    public function bark() {
        echo "$this->name is barking.
";
    }
}

$dog = new Dog();
$dog->name = "Fido";
$dog->color = "brown";
$dog->eat(); // 輸出: Fido is eating.
$dog->sleep(); // 輸出: Fido is sleeping.
$dog->bark(); // 輸出: Fido is barking.

?? ?????? protected ???? ???? $name ? $color ??? ?????. ?, ?? ???? ?? ??? ???? ???? ? ??? ??? ????? ?? ???? ? ????. ?? ?????? public ???? ???? bark() ???? ?????, ?? ??? ??? ?? ???? ???? ? ??? ?????.

2. ???

???? ??? ?? ??? ??? ? ??? ?? ?????. ?? ?? ??????? ???? ????? ???? ??? ?? ?? ?? ???? ?? ???? ??? ? ??? ?????.

?? ??, ?? ??? ???? show($animal) ???? ?? ??? ??? Zoo? ??? ? ????. ?? ???? ???? ?? ??? ?? ??? show() ???? ??? ? ????.

class Zoo {
    public function show($animal) {
        $animal->eat();
        $animal->sleep();
    }
}

$dog = new Dog();
$dog->name = "Fido";
$dog->color = "brown";

$cat = new Cat();
$cat->name = "Fluffy";
$cat->color = "white";

$zoo = new Zoo();
$zoo->show($dog); // 輸出: Fido is eating. Fido is sleeping.
$zoo->show($cat); // 輸出: Fluffy is eating. Fluffy is sleeping.

? ???? Animal ????? ???? eat() ???? ????? ??? ??? ??? Cat? ??????. ?? ??? ??? show() ???? ??? ? ??? ? ? Animal ???? ?? ?????? ???? ??? ? ????.

3. ?????

?????? ??? ???? ????? ?? ??? ?? ?????. PHP?? ???? ?? ?? ?? ??? ???? ?? ?? ??? ?????? ??? ? ????.

?? ??, ?? ??? ???? ?? talk() ???? ?? Speakable ?????? ??? ? ????. ?? ?? ?? ??? ???? ? ?????? ????? ? ? ????.

interface Speakable {
    public function speak();
}

class Dog extends Animal implements Speakable {
    public function bark() {
        echo "$this->name is barking.
";
    }
    
    public function speak() {
        $this->bark();
    }
}

class Cat extends Animal implements Speakable {
    public function meow() {
        echo "$this->name is meowing.
";
    }
    
    public function speak() {
        $this->meow();
    }
}

$dog = new Dog();
$dog->name = "Fido";
$dog->color = "brown";
$dog->speak(); // 輸出: Fido is barking.

$cat = new Cat();
$cat->name = "Fluffy";
$cat->color = "white";
$cat->speak(); // 輸出: Fluffy is meowing.

? ???? talk() ???? ?? Speakable ?????? ?????. ?? ?? Dog ? Cat ???? ? ?????? ???? ?? talk() ???? ????? ???. ?? ??? ??? ???? ??? ?? ?? ? ?? ??? ??? ?? talk() ???? ??? ? ????.

??, ??? ? ?????? PHP ?? ?? ?????? ? ?? ?? ?????. ?? ?? ??? ? ? ?? ? ???? ?? ????? ???? ??? ? ????. ??? ??? ???? PHP? ?? ?? ????? ??? ? ?? ??? ? ????.

? ??? ??, ??? ? ?????: PHP? ? ?? ?? ?? ?? ??? ?? ?????. ??? ??? PHP ??? ????? ?? ?? ??? ?????!