PHP子类不会覆盖新值

Question

I am very new to OOP and trying to figure it out. I have the following code for a Mammal class which I plan to develop further. I have a child class Bear that echoes the correct values, but I can't over-write the $name, $move, $ear, or $sound values in the subclass Grizzly.

abstract class Mammal
{
    protected $name;
    protected $limbs;
    protected $offspring = 'live';
    protected $move;
    protected $eat;
    protected $sound;

    protected function __construct($name, $limbs, $offspring, $move, $eat, $sound) {
        $this->name = $name;
        $this->limbs = $limbs;
        $this->offspring = $offspring;
        $this->move = $move;
        $this->eat = $eat;
        $this->sound = $sound;
    }

    public function getOutput() {
        echo "The {$this->name} has four {$this->limbs}. The offspring is birthed {$this->offspring} and move by {$this->move}. They eat {$this->eat} and talk by {$this->sound}.";
    }
}

class Bear extends Mammal
{
    public function __construct() {
        Mammal::__construct('bear', 'claws', $this->offspring, '', '', '');
    }
}

class Grizzly extends Bear
{
    public function __construct() {
        Bear::__construct('grizzly bear', 'claws', $this->offspring, 'lumbering', 'salmon', 'roaring');
    }
}

$grizzly = new Grizzly;
$grizzly->getOutput();

The output I am trying to get is: "The grizzly bear has four claws. The offspring is birthed live and move by lumbering. They eat salmon and talk by roaring." I appreciate any help!

Answer 1

The reason is that your bear class does not seem to take variables.

class Bear extends Mammal
{
    public function __construct() { //See, this constructor takes nothing
        Mammal::__construct('bear', 'claws', $this->offspring, '', '', '');
    }
}

Here is what I did to make it work

class Bear extends Mammal
{
    public function __construct($bear = 'bear') {//right hear
        Mammal::__construct($bear, 'claws', $this->offspring, '', '', '');
    }
}

Your code in codepad.org with my little change

Note: That's how I made it work