PHP面向对象程序设计高级特性详解(接口,继承,抽象类,析构,克隆等)

<?php
class staticexample {
  static public $anum = 0; // 静态共有属性
  static public function sayhello() { // 静态共有方法
    print "hello";
  }
}
print staticexample::$anum;
staticexample::sayhello();
?>

<?php
class staticexample {
  static public $anum = 0;
  static public function sayhello() { // 这里的static 和 public的顺序可以颠倒
    self::$anum++;
    print "hello (".self::$anum.")\n"; // self 指向当前类, $this指向当前对象。
  }
}
staticexample::sayhello();
staticexample::sayhello();
staticexample::sayhello();
?>

hello (1)
hello (2)
hello (3)

<?php
class shopproduct {
  const available   = 0; // 只能用大写字母命名常量
  const out_of_stock  = 1;
  public $status;
}
print shopproduct::available;
?>

<?php
interface chargeable { // 接口,抽象类是介于基类与接口之间的东西
  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 { // 继承类与接口
  // ...
}
?>

<?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 );
?>

document object
(
)

<?php
abstract class domainobject {
  private $group; // 私有属性group
  public function __construct() {
    $this->group = static::getgroup();//static 静态类
  }
  public static function create() {
    return new static();
  }
  static function getgroup() { // 静态方法
    return "default";
  }
}
class user extends domainobject {
}
class document extends domainobject {
  static function getgroup() { // 改变了内容
    return "document";
  }
}
class spreadsheet extends document { // 继承之后，group也就与document相同了
}
print_r(user::create());
print_r(spreadsheet::create());
?>

user object
(
  [group:domainobject:private] => default
)
spreadsheet object
(
  [group:domainobject:private] => document
)

<?php
final class checkout { // 终止类的继承
  // ...
}
class illegalcheckout extends checkout {
  // ...
}
$checkout = new checkout();
?>

<?php
class checkout {
  final function totalize() {
    // calculate bill
  }
}
class illegalcheckout extends checkout {
  function totalize() { // 不能重写final方法
    // change bill calculation
  }
}
$checkout = new checkout();
?>

<?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() { // 析构函数
    if ( ! empty( $this->id ) ) {
      // save person data
      print "saving person\n";
    }
    if ( empty( $this->id ) ) {
      // save person data
      print "do nothing\n";
    }
  }
}
$person = new person( "bob", 44 );
$person->setid( 343 );
$person->setid( '' ); // 最后执行析构函数，使用完之后执行
?>

<?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() { // 克隆时候执行
    $this->id = 0;
  }
}
$person = new person( "bob", 44 );
$person->setid( 343 );
$person2 = clone $person;
print_r( $person );
print_r( $person2 );
?>

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 { // 账户类
  public $balance; // 余额
  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 ) ); // 以类对象作为参数
$person->setid( 343 );
$person2 = clone $person;
// give $person some money
$person->account->balance += 10;
// $person2 sees the credit too
print $person2->account->balance; // person的属性account也是一个类，他的属性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; // 打印时候集中处理
// bob (age 44)
?>