class Person {
    private $nickname;
    private $year_of_birth;
    private $gender;
    
    public function __construct ($nickname, $year_of_birth, $gender)      {
        $this-> nickname = $nickname;
        $this -> year_of_birth = $year_of_birth;
        $this ->gender = $gender;
    }
    
    public function get_nickname(){
    return $this->nickname;
    }
    
    public function get_year(){
    return $this->year;
    }
    
    public function get_gender(){
    return $this->gender;
    }
    
    public function calculate_age(){
       return date('Y') - $this->year_of_birth;
    }
    
    } 
  
?>