我可以在 PHP 中将对象声明为类中的数据成员吗？

Question

所以我得到了一个抽象类 Bee：

    abstract class Bee{
  private $name;
  private $number;
  private $health;

  public function __construct() {
  }
  /**
   * Functii set/get.
   */
  public function getName() { return $this->name; }
  public function setName($value) { $this->name = $value; }

  public function getNumber() { return $this->number; }
  public function setNumber($value) { $this->number = $value; }

  public function getHealth() { return $this->health; }
  public function setHealth($value) { $this->health = $value; }

  abstract public function hitted(); ///
}

另外 3 个类（Queen、Worker 和 Drone）扩展了 Bee 类

/

**
 * Queen.
 */
class Queen extends Bee
{

  public function __construct() ///initializarea valorile Queen.
  {
    $this->setName("Queen");
    $this->setHealth(100);
      $this->setNumber(1);
  }


  public function hitted() /// Evenimentele declansate de primirea atacurilor.
  {
        $this->setHealth($this->getHealth() - 8);

  }
}

/**
 * Worker.
 */
class Worker extends Bee
{

  public function __construct() ///initializarea valorile Worker.
  {
    $this->setName("Worker");
    $this->setHealth(75);
      $this->setNumber(5);
  }


  public function hitted() /// Evenimentele declansate de primirea atacurilor.
  {
        $this->setHealth($this->getHealth() - 10);

  }
}

/**
 * Drone.
 */
class Drone extends Bee
{

  public function __construct() ///initializarea valorile Drone.
  {
    $this->setName("Drone");
    $this->setHealth(50);
      $this->setNumber(8);
  }


  public function hitted() /// Evenimentele declansate de primirea atacurilor.
  {
        $this->setHealth($this->getHealth() - 12);

  }
}

当我使用以下数据成员声明 Class Swamp 时出现错误：

class Swarm{

    public $arr = array();
    public $queen = new Queen();
    public $worker = new Worker();
    public $drone = new Drone();

  public function __construct() {
    
  }


}

这是我的错误：

致命错误：常量表达式在 C:\xampp\htdocs\The Bee Game\background.php 在第 93 行

第 93 行在 Swamp 类中：

public $queen = new Queen(); 

Answer 1

只需在构造函数中进行初始化

class Swarm {
    public $arr = array();
    public $queen;
    public $worker;
    public $drone;

    public function __construct() {
        $this->queen = new Queen();
        $this->worker = new Worker();
        $this->drone = new Drone();
    }
}