所以我昨天才开始学习如何使用memcache。所以还有很多事情要做。到目前为止,我已经了解了如何安装它,并看到了一些有关如何使用它的教程。但他们都解释了如何静态地输入它。我在类中执行所有数据库查询,并运行 foreach 循环返回的数据。我让它工作,没有任何编译错误,但内存缓存实际上无法工作。我很困惑为什么。我的类(class)就是这样设置的。
class Feed extends Database
{
private $Memcache;
public function __construct()
{
parent::__construct();
$this->Memcache = new Memcache;
} //end __construct
public function getFeed ($var)
{
$feed = array(); //Initialize an empty array
$this->Memcache->connect('localhost', 11211);
$key = "SELECT col FROM table WHERE value = " . $var . " ORDER BY timestamp DESC LIMIT 30";
$cache = $this->Memcache->get($key);
if ($cache)
{
$feed = '';
}
else
{
//Query the database
$Statement = $this->Database->prepare("SELECT col FROM table WHERE value = ? ORDER BY timestamp DESC LIMIT 30");
$Statement->execute(array($var));
while($row = $Statement->fetch(PDO::FETCH_ASSOC))
{
$feed[] = array("row1" => $row["col1"],
"row2" => $row["col2"] );
}
$this->Memcache->set($key, $row, 0, 40); // Store the result of the query for 40 seconds
}
return $feed;
} //end getFeed
} //end Feed
输出设置如下
<?php foreach ($Feed->getFeed($var) as $feed): ?>
<p><?php echo $feed["row1"]; ?></p>
<?php endforeach; ?>
很明显,如果内存缓存正在工作,它们将是一个编译错误,因为我使用 foreach 循环运行 $feed 。由于我对内存缓存的了解有限,你们知道为什么它不检索数据吗?
非常感谢您!
最佳答案
来自内存缓存 protocol description :
Keys
Data stored by memcached is identified with the help of a key. A key is a text string which should uniquely identify the data for clients that are interested in storing and retrieving it. Currently the length limit of a key is set at 250 characters (of course, normally clients wouldn't need to use such long keys); the key must not include control characters or whitespace.
您的 key 包含空格字符,因此失败。您可以检查这一点,因为 Memcache::set() 在失败时返回 FALSE。
防止这种情况的简单方法:从您的 $key 创建 MD5 哈希并将其用作 $key:
$key = md5("SELECT col FROM table WHERE value = " . $var . " ORDER BY timestamp DESC LIMIT 30");
注意:Memcache 值不能大于 1MB。
关于php - 在类中使用 memcache,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/15347704/