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# LXXXVI. 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.

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

本 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.

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。

表 1. 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

有关 PHP_INI_* 常量进一步的细节与定义参见附录 H。

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.

# 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

表 2. MemCache Constants

Name | Description
--- | ---
`MEMCACHE_COMPRESSED` (integer) | Used to turn on-the-fly data compression on with Memcache::set(), Memcache::add() 和 Memcache::replace().

# 范例

例 1. memcache extension overview example

`<?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_object, false, 10) 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);
?>`

In the above 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.

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