PHP: Accessing protected var from child class

Question

I'm learning PHP and I'm stuck i the following code:

<?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);

?>

This is what I got:

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

This looks strange to me as I should access protected vars and functions from child classes.

Could please someone explain where I'm wrong?

Many thanks.

Daan · Accepted Answer · 2016-09-05 08:00:24Z

2

Protected variables can indeed be accessed from the child class. However you aren't accessing your variable from inside the child class.

If you make the variables public you can access them from outside the class.

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

Example:

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.

edited Sep 5, 2016 at 8:00

answered Sep 5, 2016 at 7:07

Daan

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5 Comments

Alby11 Over a year ago

Thanks @Daan but I not sure I get it. You mean I'm trying to access it from an instance ($poppy) of the subclass and not from the sublass definition (class poodle extends...)?

Daan Over a year ago

It means you're not accessing it from inside the dog class but from the outside.

Alby11 Over a year ago

I'm very sorry but I don't understand. I'm trying to access $Name from the poodle subclass, which inherits from dog class. I create an instance of poodle ($poppy) and I try to change the protected var $Name. I understand I can't do this with a private var but $Name is protected. So as $poppy is an instance of poodle class, I should be able to modify the protected parent's var. Thanks for you patience.

Daan Over a year ago

I've added an example, hopefully this will clear things up.

Alby11 Over a year ago

Thank you very much, now I understand! Have a nice day.,

Matthieu · Accepted Answer · 2016-09-05 07:10:53Z

0

You can't access the property 'Words', you need to make it public

edited Sep 5, 2016 at 7:10

answered Sep 5, 2016 at 7:09

Matthieu

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Comments

Professor Abronsius · Accepted Answer · 2016-09-05 07:11:57Z

0

you could add magic methods to your class - that would allow you to access and manipulate the private properties from outside the class.

class foo{
    private $bah;

    public function __construct(){
        $this->bah='hello world';
    }
    public function __get( $name ){
        return $this->$name;
    }
    public function __set( $name,$value ){
        $this->$name=$value;
    }
    public function __isset( $name ){
        return isset( $this->$name );
    }
    public function __unset( $name ){
        unset( $this->$name );  
    }
}

$foo=new foo;
echo $foo->bah;

$foo->bah='banana';
echo $foo->bah;

answered Sep 5, 2016 at 7:11

Professor Abronsius

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