PHP类-如何使类知道父级值

Question

<?php

class FirstClass{
    public static $second;  
    public static $result = 'not this =/';
    public function __construct(){
        $this->result = 'ok';
        $this->second = new SecondClass();
    }   

    public function show(){
        echo $this->second->value;
    }
}

class SecondClass extends FirstClass{
    public $value;
    public function __construct(){
        $this->value = parent::$result; //Make it get "ok" here
    }
}

$temp = new FirstClass();
$temp->show(); //It will show: "not this =/"

?>

How can I make it to print "ok"?

I mean, the SecondClass should know what FirstClass set as result, see?

Answer 1

Replace $this->result = 'ok'; with self::$result = 'ok'; in FirstClass constructor.

Btw, the code is terrible. You're mixing static and instance variables, and extend classes but don't use benefits extension provides.

Answer 2

you need to reference the static as self::$result in the first class.

Below should do what you want...

<?php

class FirstClass{
    public static $second;  
    public static $result = 'not this =/';
    public function __construct(){
        self::$result = 'ok';
        $this->second = new SecondClass();
    }   

    public function show(){
        echo $this->second->value;
    }
}

class SecondClass extends FirstClass{
    public $value;
    public function __construct(){
        $this->value = parent::$result; //Make it get "ok" here
    }
}

$temp = new FirstClass();
$temp->show(); //It will show: "not this =/"

?>