Inheritance in PHP OOP

<?php

class Human
{
    private $name;
    private $gender;

    public function __construct($name, $gender)
    {
        $this->name = $name;
        $this->gender = $gender;
    }

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

    public function setGender($gender)
    {
        $this->gender = $gender;
    }

    public function getName()
    {
        return $this->name;
    }

    public function setName($name)
    {
        $this->name = $name;
    }
}

class Student extends Human
{

    private $id;
    private $score;

    public function __construct($id, $score, $name, $gender)
    {
        parent::__construct($name, $gender);
        $this->id = $id;
        $this->score = $score;
    }

    public function getId()
    {
        return $this->id;
    }

    public function setId($id)
    {
        $this->id = $id;
    }

    public function getScore()
    {
        return $this->score;
    }

    public function setName($score)
    {
        $this->score = $score;
    }
}

class Employee extends Human
{

    private $id;
    private $salary;

    public function __construct($id, $salary, $name, $gender)
    {
        parent::__construct($name, $gender);
        $this->id = $id;
        $this->salary = $salary;
    }

    public function getId()
    {
        return $this->id;
    }

    public function setId($id)
    {
        $this->id = $id;
    }

    public function getSalary()
    {
        return $this->salary;
    }

    public function setSalary($salary)
    {
        $this->salary = $salary;
    }
}

$student = new Student('st01', 6.7, 'name 1', 'male');
echo '<h4>Student Info</h4>';
echo 'id: ' . $student->getId();
echo '<br>name: ' . $student->getName();
echo '<br>gender: ' . $student->getGender();
echo '<br>score: ' . $student->getScore();

$employee = new Employee('e01', 1000, 'name 2', 'female');
echo '<h4>Employee Info</h4>';
echo 'id: ' . $employee->getId();
echo '<br>name: ' . $employee->getName();
echo '<br>gender: ' . $employee->getGender();
echo '<br>score: ' . $employee->getSalary();


?>

Output

Student Info
id: st01
name: name 1
gender: male
score: 6.7

Employee Info
id: e01
name: name 2
gender: female
score: 1000