PHP:从子类访问 protected var

Question

我正在学习 PHP，但遇到了以下代码:

<?php

class dogtag {

    protected $Words;

}

class dog {

    protected $Name;
    protected $DogTag;

    protected function bark() {
        print "Woof!\n";
    }

}

class poodle extends dog {

    public function bark() {
        print "Yip!\n";
    }

}

$poppy = new poodle;
$poppy->Name = "Poppy";
$poppy->DogTag = new dogtag;
$poppy->DogTag->Words = "My name is
Poppy. If you find me, please call 555-1234";

var_dump($poppy);

?>

这是我得到的:

PHP Fatal error:  Uncaught Error: Cannot access protected property poodle::$Name

这对我来说很奇怪，因为我应该从子类访问 protected 变量和函数。

谁能解释一下我哪里错了？

非常感谢。

Answer 1

确实可以从子类访问 protected 变量。但是，您没有从子类内部访问您的变量。

如果您将变量设置为public，您就可以从类外部访问它们。

文档:http://php.net/manual/en/language.oop5.visibility.php

例子:

Class Dog {

   private $privateProperty = "private"; //I can only be access from inside the Dog class
   protected $protectedProperty = "protected"; //I can be accessed from inside the dog class and all child classes
   public $publicProperty = "public"; //I can be accessed from everywhere.

}


Class Poodle extends Dog {

   public function getProtectedProperty(){
       return $this->protectedProperty; //This is ok because it's inside the Poodle (child class);
   }

}

$poodle = new Poodle;
echo $poodle->publicProperty; //This is ok because it's public
echo $poodle->getProtectedProperty(); //This is ok because it calls a public method.