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Memcache Functions

简介

Memcache module provides handy procedural and object oriented interface to memcached, highly effective caching daemon, which was especially designed to decrease database load in dynamic web applications.

The Memcache module also provides a session handler (memcache).

More information about memcached can be found at » http://www.danga.com/memcached/.

需求

This module uses functions of » zlib to support on-the-fly data compression. Zlib is required to install this module.

PHP 4.3.3 or newer is required to use the memcache extension.

安装

» PECL 扩展未绑定于 PHP 中。 安装此 PECL 扩展库的信息可在手册中标题为 PECL 扩展库安装的一章中找到。 更多信息如新版本,下载,源文件,维护者信息以及更新日志等可以在这里找到: » http://pecl.php.net/package/memcache.

In order to use these functions you must compile PHP with Memcache support by using the --enable-memcache[=DIR] option. You may optionally disable memcache session handler support by specifying --disable-memcache-session.

Windows users will enable php_memcache.dll inside of php.ini in order to use these functions. 可以从 » PHP 下载页面或者 » http://snaps.php.net/ 下载此 PECL 扩展的 DLL 文件。

运行时配置

这些函数的行为受 php.ini 的影响。

Memcache Configuration Options
Name Default Changeable Changelog
memcache.allow_failover "1" PHP_INI_ALL Available since memcache 2.0.2.
memcache.max_failover_attempts "20" PHP_INI_ALL Available since memcache 2.1.0.
memcache.chunk_size "8192" PHP_INI_ALL Available since memcache 2.0.2.
memcache.default_port "11211" PHP_INI_ALL Available since memcache 2.0.2.
memcache.hash_strategy "standard" PHP_INI_ALL Available since memcache 2.2.0.
memcache.hash_function "crc32" PHP_INI_ALL Available since memcache 2.2.0.
session.save_handler "files" PHP_INI_ALL Supported since memcache 2.1.2
session.save_path "" PHP_INI_ALL Supported since memcache 2.1.2
有关 PHP_INI_* 常量进一步的细节与定义参见php.ini 配置选项

以下是配置选项的简要解释。

memcache.allow_failover boolean

Whether to transparently failover to other servers on errors.

memcache.max_failover_attempts integer

Defines how many servers to try when setting and getting data. Used only in conjunction with memcache.allow_failover.

memcache.chunk_size integer

Data will be transferred in chunks of this size, setting the value lower requires more network writes. Try increasing this value to 32768 if noticing otherwise inexplicable slowdowns.

memcache.default_port string

The default TCP port number to use when connecting to the memcached server if no other port is specified.

memcache.hash_strategy string

Controls which strategy to use when mapping keys to servers. Set this value to consistent to enable consistent hashing which allows servers to be added or removed from the pool without causing keys to be remapped. Setting this value to standard results in the old strategy being used.

memcache.hash_function string

Controls which hash function to apply when mapping keys to servers, crc32 uses the standard CRC32 hash while fnv uses FNV-1a.

session.save_handler string

Use memcache as a session handler by setting this value to memcache.

session.save_path string

Defines a comma separated of server urls to use for session storage, for example "tcp://host1:11211, tcp://host2:11211".

Each url may contain parameters which are applied to that server, they are the same as for the Memcache::addServer() method. For example "tcp://host1:11211?persistent=1&weight=1&timeout=1&retry_interval=15"

资源类型

There is only one resource type used in memcache module - it's the link identifier for a cache server connection.

预定义常量

Memcache Constants
Name Description
MEMCACHE_COMPRESSED (integer) Used to turn on-the-fly data compression on with Memcache::set(), Memcache::add()Memcache::replace().
MEMCACHE_HAVE_SESSION (integer) 1 if this Memcache session handler is available, 0 otherwise.

范例

Example#1 memcache extension overview example

In this example, an object is being saved in the cache and then retrieved back. Object and other non-scalar types are serialized before saving, so it's impossible to store resources (i.e. connection identifiers and others) in the cache.

<?php

$memcache 
= new Memcache;
$memcache->connect('localhost'11211) or die ("Could not connect");

$version $memcache->getVersion();
echo 
"Server's version: ".$version."<br/>\n";

$tmp_object = new stdClass;
$tmp_object->str_attr 'test';
$tmp_object->int_attr 123;

$memcache->set('key'$tmp_objectfalse10) or die ("Failed to save data at the server");
echo 
"Store data in the cache (data will expire in 10 seconds)<br/>\n";

$get_result $memcache->get('key');
echo 
"Data from the cache:<br/>\n";

var_dump($get_result);

?>

Example#2 Using memcache session handler

<?php

$session_save_path 
"tcp://$host:$port?persistent=1&weight=2&timeout=2&retry_interval=10,  ,tcp://$host:$port  ";
ini_set('session.save_handler''memcache');
ini_set('session.save_path'$session_save_path);

?>

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