下面是我在大约一年前发现的一个函数，它应该锁定一个memcache密钥，这样你就可以更新它的值而不会出现同时试图更新密钥的2个请求的麻烦。
这是非常基本的，但我可以用一些帮助来弄清楚如何100％使用它。我不确定的部分是它在 $ updateFunction 中传递的位置，然后传递给**
call_user_func($updateFunction, $data); // update data
之前我从未使用过call_user_func（）。根据这段代码，有人可以向我展示一个基本的例子，说明它调用的函数是什么样的（没有做任何mysql或任何东西，只是它的工作方式）。我能将多个属性传递给调用函数吗？
感谢您的帮助。另外假设我已经有一个类名称Memcache，它与 $ this-＆gt;连接有连接或对象，我是否需要更改下面函数中的任何内容才能将其添加到我的Memcache类中？一旦这个函数成为我现有的memcache类的一部分，那么该回调函数是否能够调用其他类中的方法？
希望这不要混淆。
// {{{ locked_mecache_update($memcache,$key,$updateFunction,$expiryTime,$waitUTime,$maxTries)
/**
* A function to do ensure only one thing can update a memcache at a time.
*
* Note that there are issues with the $expiryTime on memcache not being
* fine enough, but this is the best I can do. The idea behind this form
* of locking is that it takes advantage of the fact that
* {@link memcache_add()}'s are atomic in nature.
*
* It would be possible to be a more interesting limiter (say that limits
* updates to no more than 1/second) simply by storing a timestamp or
* something of that nature with the lock key (currently stores "1") and
* not deleitng the memcache entry.
*
* @param $memcache memcache the memcache object
* @param $key string the key to do the update on
* @param $updateFunction mixed the function to call that accepts the data
* from memcache and modifies it (use pass by reference).
* @param $expiryTime integer time in seconds to allow the key to last before
* it will expire. This should only happen if the process dies during update.
* Choose a number big enough so that $updateFunction will take much less
* time to execute.
* @param $waitUTime integer the amount of time in microseconds to wait before
* checking for the lock to release
* @param $maxTries integer maximum number of attempts before it gives up
* on the locks. Note that if $maxTries is 0, then it will RickRoll forever
* (never give up). The default number ensures that it will wait for three
* full lock cycles to crash before it gives up also.
* @return boolean success or failure
*/
function locked_memcache_update(
$memcache, // Memcache Object
$key, // Key to update
$updateFunction, // Function to pass key/value into to update
$expiryTime=3, // time before key expires
$waitUtime=101, // time to wait for to check for lock release
$maxTries=100000) // number of times to try to get lock
{
$lock = 'lock:'.$key;
// get the lock {{{
if ($maxTries>0) {
for ($tries=0; $tries< $maxTries; ++$tries) {
if ($memcache->add($lock,1,0,$expiryTime)) { break; }
usleep($waitUtime);
}
if ($tries == $maxTries) {
// handle failure case (use exceptions and try-catch if you need to be nice)
trigger_error(sprintf('Lock failed for key: %s',$key), E_USER_NOTICE);
return false;
}
} else {
while (!$memcache->add($lock,1,0,$expiryTime)) {
usleep($waitUtime);
}
}
// }}}
//Now we have a lock so we can update of key/value
// modify data in cache {{{
$data = $memcache->get($key, $flag);
call_user_func($updateFunction, $data); // update data
$memcache->set($key, $data, $flag);
// }}}
// Update complete so we release our lock
// clear the lock
$memcache->delete($lock,0);
return true;
}
// }}}
?>
更新
这是我现有的Memcache类，我想将其与
集成<?PHP
class MemCache
{
// Memcache object
public $connection;
function __construct()
{
$this->connection = new MemCache;
}
// Set a key/value to memcache with Expire time
function store($key, $data, $ttl)
{
return $this->connection->set($key, $data, 0, $ttl);
}
// Retrieve a Value from Memcache with a KEY
function fetch($key)
{
return $this->connection->get($key);
}
// DELETE a Key/Value from Memcache with a KEY
function delete($key)
{
return $this->connection->delete($key);
}
// Add a server connection to memcache
function addServer($host, $port = 11211, $weight = 10)
{
$this->connection->addServer($host, $port, true, $weight);
}
// Clear all memcache data
function flush()
{
return $this->connection->flush();
}
// Show Memcache stats
function stats()
{
return statDetails($this->connection->getStats());
}
// Show Memcache stats in a table
function statDetails($status)
{
echo "<table border='1'>";
echo "<tr><td>Memcache Server version:</td><td> " . $status["version"] .
"</td></tr>";
echo "<tr><td>Process id of this server process </td><td>" . $status["pid"] .
"</td></tr>";
echo "<tr><td>Number of seconds this server has been running </td><td>" . $status["uptime"] .
"</td></tr>";
echo "<tr><td>Accumulated user time for this process </td><td>" . $status["rusage_user"] .
" seconds</td></tr>";
echo "<tr><td>Accumulated system time for this process </td><td>" . $status["rusage_system"] .
" seconds</td></tr>";
echo "<tr><td>Total number of items stored by this server ever since it started </td><td>" .
$status["total_items"] . "</td></tr>";
echo "<tr><td>Number of open connections </td><td>" . $status["curr_connections"] .
"</td></tr>";
echo "<tr><td>Total number of connections opened since the server started running </td><td>" .
$status["total_connections"] . "</td></tr>";
echo "<tr><td>Number of connection structures allocated by the server </td><td>" .
$status["connection_structures"] . "</td></tr>";
echo "<tr><td>Cumulative number of retrieval requests </td><td>" . $status["cmd_get"] .
"</td></tr>";
echo "<tr><td> Cumulative number of storage requests </td><td>" . $status["cmd_set"] .
"</td></tr>";
$percCacheHit = ((real)$status["get_hits"] / (real)$status["cmd_get"] * 100);
$percCacheHit = round($percCacheHit, 3);
$percCacheMiss = 100 - $percCacheHit;
echo "<tr><td>Number of keys that have been requested and found present </td><td>" .
$status["get_hits"] . " ($percCacheHit%)</td></tr>";
echo "<tr><td>Number of items that have been requested and not found </td><td>" .
$status["get_misses"] . "($percCacheMiss%)</td></tr>";
$MBRead = (real)$status["bytes_read"] / (1024 * 1024);
echo "<tr><td>Total number of bytes read by this server from network </td><td>" .
$MBRead . " Mega Bytes</td></tr>";
$MBWrite = (real)$status["bytes_written"] / (1024 * 1024);
echo "<tr><td>Total number of bytes sent by this server to network </td><td>" .
$MBWrite . " Mega Bytes</td></tr>";
$MBSize = (real)$status["limit_maxbytes"] / (1024 * 1024);
echo "<tr><td>Number of bytes this server is allowed to use for storage.</td><td>" .
$MBSize . " Mega Bytes</td></tr>";
echo "<tr><td>Number of valid items removed from cache to free memory for new items.</td><td>" .
$status["evictions"] . "</td></tr>";
echo "</table>";
}
}
?>
答案 0 :(得分：2)
documentation of call_user_func()包含指向callback pseudo-type的链接。简而言之，它是函数名称或数组。数组必须包含两个字符串（类名和函数名 - 静态函数的回调）或对象和字符串（对象和调用该对象的方法 - 用于成员函数）。以下是文档中的示例：
<?php // An example callback function function my_callback_function() { echo 'hello world!'; } // An example callback method class MyClass { static function myCallbackMethod() { echo 'Hello World!'; } } // Type 1: Simple callback call_user_func('my_callback_function'); // Type 2: Static class method call call_user_func(array('MyClass', 'myCallbackMethod')); // Type 3: Object method call $obj = new MyClass(); call_user_func(array($obj, 'myCallbackMethod')); // Type 4: Static class method call (As of PHP 5.2.3) call_user_func('MyClass::myCallbackMethod'); // Type 5: Relative static class method call (As of PHP 5.3.0) class A { public static function who() { echo "A\n"; } } class B extends A { public static function who() { echo "B\n"; } } call_user_func(array('B', 'parent::who')); // A ?>
还有一件事：add($lock,...和get()之间的锁定可能是interrupted。使用increment()和decrement()可以解决这个问题。
答案 1 :(得分：1)
不是直接答案，但值得注意的是，您实际上并不需要使用call_user_func - 您只需调用变量函数：
function ham($jam) {
echo $jam;
}
$bar = 'eggs';
$foo = 'ham';
$foo($bar);
这也适用于实例化对象：
$bees->$honey($sting);
docs中有更多信息。