<?php
class StaticExample {
    static public $aNum = 0; // 靜態共有屬性
    static public function sayHello() { // 靜態共有方法
        print "hello";
    }
}

print StaticExample::$aNum;
StaticExample::sayHello();
?>
輸出：0    hello

<?php

class StaticExample {
    static public $aNum = 0;
    static public function sayHello() { // 這裡的static 和 public的順序可以顛倒
        self::$aNum++;
        print "hello (".self::$aNum.")
"; // self 指向當前類, $this指向當前物件。
    }
}

StaticExample::sayHello();
StaticExample::sayHello();
StaticExample::sayHello();
?>
輸出：
hello (1)
hello (2)
hello (3)

<?php
class ShopProduct {
    const AVAILABLE      = 0; // 只能用大寫字母命名常量
    const OUT_OF_STOCK   = 1;
    public $status;
}
print ShopProduct::AVAILABLE;
?>
輸出：0

<?php
interface Chargeable { // 介面,抽象類是介於基類與介面之間的東西
    public function getPrice();
}

class ShopProduct implements Chargeable {
    // ...
    protected $price;
    // ...

    public function getPrice() {
        return $this->price;
    }
    // ...

}

$product = new ShopProduct();

?>

<?php
class TimedService{ }
interface Bookable{ }
interface Chargeable{ }

class Consultancy extends TimedService implements Bookable, Chargeable { // 繼承類與介面
    // ...
}
?>

<?php

abstract class DomainObject {

}

class User extends DomainObject {
    public static function create() {
        return new User();        
    }
}

class Document extends DomainObject {
    public static function create() {
        return new Document();        
    }
}

$document = Document::create();
print_r( $document );
?>
輸出：
Document Object
(
)

<?php
abstract class DomainObject {
    private $group; // 私有屬性group
    public function __construct() {
        $this->group = static::getGroup();//static 靜態類
    }

    public static function create() {
        return new static();        
    }

    static function getGroup() { // 靜態方法
        return "default"; 
    }
}

class User extends DomainObject {
}

class Document extends DomainObject {
    static function getGroup() { // 改變了內容
        return "document"; 
    }
}

class SpreadSheet extends Document { // 繼承之後，group也就與document相同了
}

print_r(User::create());
print_r(SpreadSheet::create());
?>
輸出：
User Object
(
    [group:DomainObject:private] => default
)
SpreadSheet Object
(
    [group:DomainObject:private] => document
)

<?php
final class Checkout { // 終止類的繼承
    // ...
}

class IllegalCheckout extends Checkout {
    // ...
}

$checkout = new Checkout();

?>
輸出：
Fatal error: Class IllegalCheckout may not inherit from final class (Checkout)

<?php
class Checkout {
    final function totalize() {
        // calculate bill
    }
}


class IllegalCheckout extends Checkout {
    function totalize() { // 不能重寫final方法
        // change bill calculation
    }
}

$checkout = new Checkout();

?>
輸出：
Fatal error: Cannot override final method Checkout::totalize() 

<?php
class Person {
    protected $name;    
    private $age;    
    private $id;    

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

    function setId( $id ) {
        $this->id = $id;
    }
    
    function __destruct() { // 解構函式
        if ( ! empty( $this->id ) ) {
            // save Person data
            print "saving person
";
        }

        if ( empty( $this->id ) ) {
            // save Person data
            print "do nothing
";
        }
    }
}

$person = new Person( "bob", 44 );
$person->setId( 343 );
$person->setId( `` ); // 最後執行解構函式，使用完之後執行

?>
輸出：
do nothing

<?php
class Person {
    private $name;    
    private $age;    
    private $id;    

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

    function setId( $id ) {
        $this->id = $id;
    }
    
    function __clone() { // 克隆時候執行
        $this->id = 0;
    }
}

$person = new Person( "bob", 44 );
$person->setId( 343 );
$person2 = clone $person;
print_r( $person );
print_r( $person2 );

?>
輸出：
Person Object
(
    [name:Person:private] => bob
    [age:Person:private] => 44
    [id:Person:private] => 343
)
Person Object
(
    [name:Person:private] => bob
    [age:Person:private] => 44
    [id:Person:private] => 0
)

<?php
class Account { // 賬戶類
    public $balance; // 餘額
    function __construct( $balance ) {
        $this->balance = $balance;
    }
}

class Person {
    private $name;
    private $age;
    private $id;
    public $account;

    function __construct( $name, $age, Account $account ) {
        $this->name = $name;
        $this->age  = $age;
        $this->account = $account;
    }

    function setId( $id ) {
        $this->id = $id;
    }

    function __clone() {
        $this->id   = 0;
    }
}

$person = new Person( "bob", 44, new Account( 200 ) ); // 以類物件作為引數
$person->setId( 343 );
$person2 = clone $person;

// give $person some money
$person->account->balance += 10;
// $person2 sees the credit too
print $person2->account->balance; // person的屬性account也是一個類，他的屬性balance的值是210

// output:
// 210

?>

<?php

class Person {
    function getName()  { return "Bob"; }
    function getAge() { return 44; }
    function __toString() {
        $desc  = $this->getName()." (age ";
        $desc .= $this->getAge().")";
        return $desc;
    }
}

$person = new Person();
print $person; // 列印時候集中處理
// Bob (age 44)
?>