Use the class as a data type. Real PHP example

Let’s create a simple base class, for example it will be a fictional game:

class Animal {
	public $name;
	public $health;
	public $alive;
	protected $power;//can used by childs

	public function __construct(string $name, int $health, int $power){
		$this->name = $name;
		$this->health = $health;
		$this->power = $power;
		$this->alive = true;
	}

	public function calcDamage(){
		return $this->power * (mt_rand(100, 300) / 200);
	}

	public function applyDamage(int $damage){
		$this->health -= $damage;//andlog $this->health = $this->health - $damage;

		if($this->health <= 0){
			$this->health = 0;
			$this->alive = false;
		}
	}
}

Now we inherit our parent class:

class Dog extends Animal{
}

class Cat extends Animal{
	private $lifes;

	public function __construct(string $name, int $health, int $power){
		parent::__construct($name, $health, $power);
		$this->lifes = 9;
		$this->baseHealth = $health;
	}

	public function applyDamage(int $damage){
		parent::applyDamage($damage);
		
		if(!$this->alive && $this->lifes > 1){
			$this->lifes--;
			$this->alive = true;
			$this->health = $this->baseHealth;
		}
	}
}

Let’s create another child class with a character:

class Mouse extends Animal{
	private $hiddenLevel;

	public function __construct(string $name, int $health, int $power){
		parent::__construct($name, $health, $power);
		$this->hiddenLevel = 0.95;
	}

	public function setHiddenLevel(float $level){
		$this->hiddenLevel = $level;
	}

	public function applyDamage(int $damage){
		if((mt_rand(1, 100) / 100) > $this->hiddenLevel){
			parent::applyDamage($damage);
		}
	}
}

Now lets create our game core:

class GameCore{
	private $units;

	public function __construct(){
		$this->units = [];
	}

	public function addUnit(Animal $unit){
		$this->units[] = $unit;
	}

	public function run(){
		$i = 1;

		while(count($this->units) > 1){
			echo "Round $i <br>";
			$this->nextTick();
			$i++;
			echo '<hr>';
		}
	}

	public function nextTick(){
		foreach($this->units as $unit){
			$damage = $unit->calcDamage();
			$target = $this->getRandomUnit($unit);
			$targetPrevHealth = $taуrget->health;
			$target->applyDamage($damage);
			echo "{$unit->name} beat {$target->name}, damage=$damage, 
				health {$targetPrevHealth} -> {$target->health}  <br>";
		}

		$this->units = array_values(array_filter($this->units, function($unit){
			return $unit->alive;
		}));
	}

	private function getRandomUnit(Animal $exclude){
		$units = array_values(array_filter($this->units, function(Animal $unit) use ($exclude){
			return $unit !== $exclude;
		}));

		return $units[mt_rand(0, count($units) - 1)];
	}
}

Now let’s run our game:

$core = new GameCore();

$core->addUnit(new Cat('Murzik', 20, 5));
$core->addUnit(new Dog('Bobik', 200, 10));
$core->addUnit(new Mouse('Jerry', 10, 3));
$core->addUnit(new Cat('Garfild', 30, 4));
$core->addUnit(new Dog('Volk', 180, 9));
$core->addUnit(new Mouse('Guffy', 10, 5));

$core->run();
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