麻烦了解全局变量在类中的调用

Question

我遇到了numberOfDecks方法的问题。我尝试调用在构造函数中创建的卡片数组，但是一个错误不断出现，我传递了一个未定义的变量（$ cards）。我想因为它是一个全局变量，所以$ cards可以被调用到numberOfDecks方法。

<?php 
/* creating a deck of cards class to be used in a blackJack game*/ 

class Deck{ 

    public $cards = array(); 

    //creates an instance of a deck of cards (works) 

    public function __construct(){ 
    $values =array('2','3','4','5','6','7','8','9','10','J','Q','K','A'); 
    $suits =array('Diamond','Club','Heart','Spade'); 
     foreach ($suits as $suit) { 
     foreach($values as $value){ 
      $this->cards[] = "$value of $suit's"; 
     } 
     } 
    } 

    /*trying to add more decks to increase number of total cards 
    in my array (does not work)*/ 

    public function numberOfDecks($number){ 

    $this->cards = $cards; 
    $this->number= $number; 
    for($i = 0 ; $i < $number; $i++){ 
      array_push($cards[],$i); 
    } 
    return $cards; 

    } 
} 



$deck = new Deck();//works as expected 
$deck->numberOfDecks(3);//trouble 
$shuffled = shuffle($deck->cards);//works as expected 
var_dump($deck); 

Answer 1

您的变量$cards未定义，因为您没有声明它。

public function numberOfDecks($number){ 

$this->cards = $cards; 

您可能是想翻转分配方向。

$cards = $this->cards; 

鉴于添加甲板对象桥面总您的评论，翻转分配方向后，尝试使用array_merge

Here's a working fiddle.

<?php 

class Deck{ 

    public $cards = array(); 

    //creates an instance of a deck of cards (works) 

    public function __construct(){ 
    $values =array('2','3','4','5','6','7','8','9','10','J','Q','K','A'); 
    $suits =array('Diamond','Club','Heart','Spade'); 
     foreach ($suits as $suit) { 
     foreach($values as $value){ 
      $this->cards[] = "$value of $suit's"; 
     } 
     } 
    } 

    public function numberOfDecks($number){ 

     $cards = $this->cards; 

     $this->number = $number; 
     for($i = 0 ; $i < $number; $i++){ 
      $this->cards = array_merge($this->cards, $cards); 
     } 

    } 
} 



$deck = new Deck();//works as expected 

// how many cards are intially constructed? 
echo "count of cards in new deck: " . count($deck->cards) . "\n<br/>\n"; 

// add 3 more decks of cards 
$deck->numberOfDecks(3);//trouble 
echo "count of cards after adding 3 decks: " . count($deck->cards); 

// $shuffled = shuffle($deck->cards);//works as expected 
// var_dump($deck); 

结果输出：

新甲板上牌数：52 卡 数增加3套牌后：208