Code examples of non-forwarded calls and forwarded calls in PHP

    1)self::
    2)parent::
    3)static::
    4)forward_static_call()
    5)get_called_class()

<?php
class A {
    public static function foo() {
        static::who();
    }

    public static function who() {
        echo __CLASS__."\n";
    }
}

class B extends A {
    public static function test() {
        A::foo();
        parent::foo();
        self::foo();
    }

    public static function who() {
        echo __CLASS__."\n";
    }
}
class C extends B {
    public static function who() {
        echo __CLASS__."\n";
    }
}

C::test();
?>

A
C
C

<?php
 
class A{
    protected $value = "A value";
 
    public function printValue(){
        echo $this->value;
    }
}
class B extends A{
   protected $value = "B value";
}
$app = new B();
$app->printValue();

运行结果：B value

<?php
 
class A{
    //只有将属性定义为静态的才能使用self::进行调用
    static protected $value = "A static value ";
    public function printValue(){
        echo self::$value;
    }
}
 
class B extends A{
    static protected $value = "B static value";
}
 
$app = new B();
$app->printValue();

<?php
class A{
    static protected $value = "A static value ";
}
 
class B extends A{
    public function printValue(){
        echo self::$value;
    }
}
$app = new B();
$app->printValue();