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# LXXXVI. Memcache Functions

# Introduction

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/.

# Requirements

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.

# Installation

This PECL extension is not bundled with PHP. Information for installing this PECL extension may be found in the manual chapter titled Installation of PECL extensions. Additional information such as new releases, downloads, source files, maintainer information, and a CHANGELOG, can be located here: 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. The DLL for this PECL extension may be downloaded from either the PHP Downloads page or from http://pecl4win.php.net/

# Runtime Configuration

The behaviour of these functions is affected by settings in `php.ini`.

Table 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

For further details and definitions of the PHP_INI_* constants, see the Appendix H.

Here's a short explanation of the configuration directives.

`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.

# Resource Types

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

# Predefined Constants

Table 2. MemCache Constants

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

# Examples

Example 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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