php面向对象abstract与interface

<?php
abstract class A {

    //子类可直接使用
    public function v1() {
        echo "view A v1".PHP_EOL;
    }

    //子类可直接使用
    protected function v2() {
        echo "view A v2".PHP_EOL;
    }

    //不能使用private修饰，不然报错
    /*
    PHP Fatal error:  Abstract function A::v3() cannot be declared private
    */
    //abstract private function v3();

    //非抽象子类 一定需要实现，不然报错
    /*
    PHP Fatal error:  Class Aa contains 2 abstract methods and must therefore be declared abstract or implement the remaining methods (A::v4, A::v5) 
    */
    abstract public function v4();
    abstract protected function v5();
}

class B {

}


//不会报错
abstract class Ab extends A {

}

//一定要实现方法 v4 和 v5，不然报错
/*
PHP Fatal error:  Class Ac contains 2 abstract methods and must therefore be declared abstract or implement the remaining methods (A::v4, A::v5)
*/
/*
class Ac extends A {
}
*/

//一定要实现方法 v4 和 v5，不然报错
/*
PHP Fatal error:  Class Ad contains 2 abstract methods and must therefore be declared abstract or implement the remaining methods (A::v4, A::v5) 
*/
/*
class Ad extends Ab {
}
*/

//只能继承一个class 或 abstract class
class Aa extends A {

    public function v4() {
        echo "view A v4".PHP_EOL;
    }

    protected function v5() {
        echo "view A v5".PHP_EOL;
    }

    public function test() {
        $this->v1();
        $this->v2();
        //$this->v3();
        $this->v4();
        $this->v5();
    }
}

//不能实例化
/*
PHP Fatal error:  Uncaught Error: Cannot instantiate abstract class A 
*/
//$a = new A();
$a = new Aa();
$a->test();

<?php
interface D {
    const NAME = "常量对象属性";

    public function v1();

    //必须实现，不然报错
    /*
    PHP Fatal error:  Class Da contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (D::v2) in
    */
    //public function v2();

    //只能使用public
    /*
    PHP Fatal error:  Access type for interface method D::v3() must be omitted
    */
    //protected function v3();
    //private function v4();
}

interface E {
    //虽然不报错，呵呵
    //public function v1();
    public function v5();
}

//可以多个interface 
class Da implements D, E {
    public function v1() {
        echo "view D v1".PHP_EOL;
    }

    public function v5() {
        echo "view D v5".PHP_EOL;
    }

    public function test() {
        $this->v1();
        $this->v5();
    }
}

$d = new Da();
$d->test();