CODEWITHSUNDEEP
phpoopabstract-class
Namal
Namal

Reputation: 2071

abstract class constructors overriding confused

I have this abstract class

 abstract class Guitar {

        protected $strings;

        public function __construct($no_of_strings) {
            $this->strings = $no_of_strings;
            echo 'Guitar class constructor is called <br/>';
        }

        abstract function play();
    }

And child class, 

class Box_Guitar extends Guitar {

    public function __construct($no_of_strings) {
        echo 'Box Guitar constructor is called <br/>';
        $this->strings = $strings + 100;
    }

    public function play() {
        echo 'strumming ' . $this->strings;
    }

}

Then I initiated the class with,

$box_guitar = new Box_Guitar(6);

And my out put was

Box Guitar constructor is called

Guitar class constructor is called

strumming 106

So my question is why parent constructor is called? I didn't use Parent::__construct().

Upvotes: 0

Views: 105

Answers (2)

Namal
Namal

Reputation: 2071

Thanks @jcsanyi. There was my fault. I have another class called, 

 class Electric_Guitar extends Guitar {

    public function play() {
        return 'Plug to current : '. $this->strings;
    }
}

This has not any constructor. When I invoking objects, I used both of them.

$box_guitar = new Box_Guitar(6);
$elec_guitar = new Electric_Guitar(5);

So the abstrct constructor was called by elec_guitar object.

Upvotes: 0

jcsanyi
jcsanyi

Reputation: 8174

It's not.

When I run the code you gave above, I get this output:

Box Guitar constructor is called
Notice: Undefined variable: strings in /test/test.php on line 19

Double-check that you're not running an old version of the files or something. Did you forget to save or upload some changes?

For the record, once you figure out why you're getting the unexpected behaviour, the right way to write the Box_Guitar constructor will probably look something like this:

public function __construct($no_of_strings) {
    echo 'Box Guitar constructor is called <br/>';
    parent::__construct($no_of_strings + 100);
}

Upvotes: 1

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