我真的不明白我的数组的输出。在一开始它接缝很简单，但我已经在这个问题上花了几个小时。看代码：
public function getAllProducts($limit){
$result = mysql_query("SELECT * FROM products ORDER BY RAND() LIMIT $limit") or die(mysql_error());
$productArray = array();
$count = 0;
while($row = mysql_fetch_row($result)){
$this->id = $row[0];
$this->category_id = $row[1];
$this->title = $row[2];
$this->short_description = $row[3];
$this->long_description = $row[4];
$this->tag = $row[5];
$this->price = $row[6];
$this->weight = $row[7];
$this->stock = $row[8];
$productArray[$count] = $this;
$count++;
}
echo'<pre>';
print_r($productArray);
echo'</pre>';
return $productArray;
}
输出：
Array
(
[0] => Product Object
(
[id] => 2
[category_id] => 2
[title] => Cart�o de Pascoa
[short_description] => Short description bout this product
[long_description] => Long description about thi product but we don
[tag] => Pascoa Coelho Cart�o Cartao Card
[price] => 60,00
[weight] => 1
[stock] => 1
)
[1] => Product Object
(
[id] => 2
[category_id] => 2
[title] => Cart�o de Pascoa
[short_description] => Short description bout this product
[long_description] => Long description about thi product but we don
[tag] => Pascoa Coelho Cart�o Cartao Card
[price] => 60,00
[weight] => 1
[stock] => 1
)
)
现在，我将只在print_r函数中进行调整：
echo'<pre>';
print_r($productArray[0]);
echo'</pre>';
新输出：
Product Object
(
[id] => 1
[category_id] => 1
[title] => Cart�o de Natal
[short_description] => Short descroption about this product
[long_description] => Long description of this product. Nor used ri
[tag] => Cart�o de Natal Natal Presente de Natal
[price] => 55,00
[weight] => 1
[stock] => 1
)
再调整一次：
echo'<pre>';
print_r($productArray[1]);
echo'</pre>';
OutPut：
Product Object
(
[id] => 2
[category_id] => 2
[title] => Cart�o de Pascoa
[short_description] => Short description bout this product
[long_description] => Long description about thi product but we don
[tag] => Pascoa Coelho Cart�o Cartao Card
[price] => 60,00
[weight] => 1
[stock] => 1
)
数据库：
1 1 Cartão de Natal Short descroption about this product Long description of this product. Nor used ri Cartão de Natal Natal Presente de Natal 55,00 1 1
2 2 Cartão de Pascoa Short description bout this product Long description about thi product but we don Pascoa Coelho Cartão Cartao Card 60,00 1 1
您是否注意到当我在$ productArray中执行print_r或var_dump时输出错误，当我们执行$ productArray [0]或$ productArray [1]时，我们得到正确的输出。有人在我的代码中发现了一些错误吗？
非常感谢先进！
答案 0 :(得分：4)
在PHP5中，当对象插入数组或传递给函数时，不会复制它们。所以你只是多次将一个对象插入到数组中，然后为每个循环迭代覆盖它的属性。
你应该：
1）创建一个新的类实例：
while($row = mysql_fetch_row($result)){
$object = new self();
$object->id = $row[0];
$object->category_id = $row[1];
2）或者在将对象插入数组时克隆该对象：
$this->stock = $row[8];
$productArray[$count] = clone $this;
$count++;
}
答案 1 :(得分：2)
问题是您始终将值分配给$this，然后将其存储在数组中。对象始终存储为引用，因此您只需在$this中反复存储对$productArray对象的引用。当您最终打印数组的内容时，您只有几次包含相同的对象，其中包含您分配给它的 last 数据。
那个var_dump($productArray[0])应该可以工作似乎很可疑，也许你在覆盖值之前在循环中调用它？
答案 2 :(得分：1)
我无法完全解释这种行为，但原因是这一行：
$productArray[$count] = $this;
您正在重复使用$this special variable来存储一些静态数据。将其替换为while循环中的其他变量名称（如$data），您应该没问题：
while($row = mysql_fetch_row($result)){
$properties = array
(
'id', 'category_id', 'title', 'short_description', 'long_description'
, 'tag', 'price', 'weight', 'stock'
);
$data = (object) array_combine($properties, $row);
$productArray[$count] = $data;
$count++;
}
如果您使用$this，则每次特定对象实例更改时，数组内的数据都将更改。你会得到一种不可预知的行为（正如你已经注意到的那样）。
答案 3 :(得分：0)
$ this的使用是一个特殊变量，它始终通过引用传递Object。继续使用它将在整个循环中更改当前对象的状态，并将当前对象的引用分配给数组，这将导致数组的最终结果具有对同一对象的X个引用数。
与$ productArray [$ var]的区别只是巧合。如果你用
运行它echo '<pre>';
print_r($productArray);
echo '/n';
print_r($productArray[0]);
echo '/n';
print_r($productArray[1]);
echo '</pre>';
您应该注意到它们都是相同的对象输出。
如果您创建了一个新对象，它将按预期运行。
public function getAllProducts($limit){
$sql = "SELECT * FROM products
ORDER BY RAND()
LIMIT $limit";
$result = mysql_query($sql) or die(mysql_error());
$productArray = array();
$count = 0;
while($row = mysql_fetch_row($result)){
$that = new Product; // Whatever your product object would be or stdClass.
$that->id = $row[0];
$that->category_id = $row[1];
$that->title = $row[2];
$that->short_description = $row[3];
$that->long_description = $row[4];
$that->tag = $row[5];
$that->price = $row[6];
$that->weight = $row[7];
$that->stock = $row[8];
$productArray[$count] = $that;
$count++;
}
echo'<pre>';
print_r($productArray);
echo'</pre>';
return $productArray;
}
我会通过添加一个函数来返回一个新实例化的对象，而不是分配公共变量。如果您决定在创建对象时使用特殊方法，则可以更轻松地维护代码。
public static function getProductFromRow(Array $row) {
$that = new Product; // Whatever your product object would be.
$that->id = $row[0];
$that->category_id = $row[1];
$that->title = $row[2];
$that->short_description = $row[3];
$that->long_description = $row[4];
$that->tag = $row[5];
$that->price = $row[6];
$that->weight = $row[7];
$that->stock = $row[8];
return $that;
}
public function getAllProducts($limit) {
$sql = "SELECT * FROM products
ORDER BY RAND()
LIMIT $limit";
$result = mysql_query($sql) or die(mysql_error());
$productArray = array();
$count = 0;
while($row = mysql_fetch_row($result)){
$productArray[$count] = Product::getProductFromRow($row);
$count++;
}
return $productArray;
}