PHP中关键字与魔术方法介绍

class BaseClass {
   public function test() {
       echo "BaseClass::test() called＼n";
   }
  
   final public function moreTesting() {
       echo "BaseClass::moreTesting() called＼n";
   }
}

class ChildClass extends BaseClass {
   public function moreTesting() {
       echo "ChildClass::moreTesting() called＼n";
   }
}
// 产生 Fatal error: Cannot override final method BaseClass::moreTesting()
?>
Example #2 Final 类示例

final class BaseClass {
   public function test() {
       echo "BaseClass::test() called＼n";
   }
  
   // 这里无论你是否将方法声明为final，都没有关系
   final public function moreTesting() {
       echo "BaseClass::moreTesting() called＼n";
   }
}

class ChildClass extends BaseClass {
}
// 产生 Fatal error: Class ChildClass may not inherit from final class (BaseClass)
?>

function test()
{
    static $var1=1;
    $var1+=2;
    echo $var1.' ';
}

test();
test();
test();
?>

Class Person{
    // 定义静态成员属性
    public static $country = "中国";
    // 定义静态成员方法
    public static function myCountry() {
        // 内部访问静态成员属性
        echo "我是".self::$country."人
";
    }
}
class Student extends Person {
    function study() {
        echo "我是". parent::$country."人
";
    }
}
// 输出成员属性值
echo Person::$country."
";  // 输出：中国
$p1 = new Person();
//echo $p1->country;   // 错误写法
// 访问静态成员方法
Person::myCountry();   // 输出：我是中国人
// 静态方法也可通过对象访问：
$p1->myCountry();

// 子类中输出成员属性值
echo Student::$country."
"; // 输出：中国
$t1 = new Student();
$t1->study();    // 输出：我是中国人
?>

Class Person{
    // 定义常量
    const country = "中国";

    public function myCountry() {
        //内部访问常量
        echo "我是".self::country."人
";
    }
}

// 输出常量
echo Person::country."
";

// 访问方法
$p1 = new Person();
$p1 -> myCountry();
?>

// Declare a simple class
class TestClass
{
    public $foo;

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

    public function __toString() {
        return $this->foo;
    }
}

$class = new TestClass('Hello');
echo $class;
?>

class SubObject
{
    static $instances = 0;
    public $instance;

    public function __construct() {
        $this->instance = ++self::$instances;
    }

    public function __clone() {
        $this->instance = ++self::$instances;
    }
}

class MyCloneable
{
    public $object1;
    public $object2;

    function __clone()
    {
     
        // 强制复制一份this->object， 否则仍然指向同一个对象
        $this->object1 = clone $this->object1;
    }
}

$obj = new MyCloneable();

$obj->object1 = new SubObject();
$obj->object2 = new SubObject();

$obj2 = clone $obj;

print("Original Object:＼n");
print_r($obj);

print("Cloned Object:＼n");
print_r($obj2);

?>

session_start();
require_once 'MyClass.php';
$obj = new MyClass;
$_SESSION['obj'] = $obj;
?>

session_start();
require_once 'MyClass.php';
$_SESSION['obj']->callSomeMethod();
?>

require_once 'MyClass.php';
session_start();
$_SESSION['obj']->callSomeMethod();
?>