how to create default value for for an object? PHP

Question

let's say I have a Human class which has the variable of $gender which doesn't have any value assigned into it. Human has a constructor with the parameter of age, gender, height and weight.

I have another class called Female which inheritance from Human but now the Female class is overriding the $gender variable with a string of Female.

When I create the object let's say $f = new Female(12, 'female', 123, 40); How can I skip typing the female when creating the object?

I thought we need to create another new constructor in Female class which I did and in the Female class constructor's parameter I have age, gender = 'female', height and weight but this doesn't seem to work.

I tried leaving the gender part empty when creating the object or tried entering empty string such as "".

Can someone give me a hand please? Thanks a lot.

Code for my human class

class Human {
    protected $age = 0;   
    protected $gender;
    protected $height_in_cm;
    protected $weight_in_kg;

    function __construct($age, $gender, $heightCM, $weightKG)
    {
        $this->age = $age;
        $this->gender = $gender;
        $this->height_in_cm = $heightCM;
        $this->weight_in_kg = $weightKG;
    }

    /**
     * @return int
     */
    public function getAge()
    {
        return $this->age;
    }

    /**
     * @return string
     */
    public function getGender()
    {
        return $this->gender;
    }
}

Code for Female class

require_once('Human.php');
class Female extends Human{
    protected $gender = 'female';

    function __construct($age, $gender = 'female', $heightCM, $weightKG)
    {
        $this->age = $age;
        $this->gender = $gender;
        $this->height_in_cm = $heightCM;
        $this->weight_in_kg = $weightKG;
    }
}

$f = new Female(12,'female',123,40);
echo "Your gender is ". $f->getGender()."<br>";

Answer 1

You can simply overwrite the constructor:

abstract class Human
{
    protected $age;

    protected $gender;

    protected $height;

    protected $weight;

    public function __construct($age, $gender, $height, $weight)
    {
        $this->age = $age;
        $this->gender = $gender;
        $this->height = $height;
        $this->weight = $weight;
    }

    public function getGender()
    {
        return $this->gender;
    }
}

class Female extends Human
{
    public function __construct($age, $height, $weight)
    {
        parent::__construct($age, 'female', $height, $weight);
    }
}

$female = new Female(12, 170, 60);
echo $female->getGender();

Answer 2

I think, in you constructor

__construct($var, $gender="female", $var, $var){
//rest assignment
}

should do it

alternatively, use 3 param constructor with female already set

Answer 3

You can just set the value in the extended class:

// If it should be possible to instantiate the Human
// class then remove the "abstract" thing at set the
// "gender" property in the constructer
abstract class Human {
    protected $gender;
    protected $age;
    public function __construct($age) {
        $this->age = $age;
    }
}
class Female extends Human {
    protected $gender = "Female";
}
class Male extends Human {
    protected $gender = "Male";
}

Although this works, it really does not make that much sense. The class itself tells you what gender the human is, so you can just call $human instanceof Female.

$person = new Female(18);
if ($person instanceof Female) {
    echo "Person is female";
}

Answer 4

Simply override the constructor:

class Human {
     public function __construct($age, $gender, $height, $weight) {
     }
}

class Female extends Human {
    public function __construct($age, $height, $weight) {
         parent::__construct($age, 'Female', $height, $weight);
    }
}