class dog
{
  var $heal=100;
  var $name='Bobik';
  var $happy=100;
  var $age = 0;

  public function go_walk()
  {
   $this->heal = $this->heal - 10;
   $this->happy = $this->happy +10;
   $this->age++;
  }

  public function let_heal()
  {
   $this->heal = $this->heal + 10;
   $this->happy = $this->happy - 10;
   $this->age++;
  }
}

class human
{
  var name = 'Vova';
  var my_dog;

  publick function go_walk_dog($dog)
  {
   $dog->go_walk();
  }
}

$human1 = new human();
$human1->dog = new dog();

$human2 = new human();
$human2->go_walk_dog(&$human1->dog);