# 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.

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

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. 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. 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.

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

For further details and definitions of the PHP_INI_* constants, see the php.ini directives.

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.

`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"

## Resource Types

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

## Predefined Constants

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

## Examples

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_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);
?>`

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);
?>`

## Table of Contents

- Memcache::add — Add an item to the server
- Memcache::addServer — Add a memcached server to connection pool
- Memcache::close — Close memcached server connection
- Memcache::connect — Open memcached server connection
- memcache_debug — Turn debug output on/off
- Memcache::decrement — Decrement item's value
- Memcache::delete — Delete item from the server
- Memcache::flush — Flush all existing items at the server
- Memcache::get — Retrieve item from the server
- Memcache::getExtendedStats — Get statistics from all servers in pool
- Memcache::getServerStatus — Returns server status
- Memcache::getStats — Get statistics of the server
- Memcache::getVersion — Return version of the server
- Memcache::increment — Increment item's value
- Memcache::pconnect — Open memcached server persistent connection
- Memcache::replace — Replace value of the existing item
- Memcache::set — Store data at the server
- Memcache::setCompressThreshold — Enable automatic compression of large values
- Memcache::setServerParams — Changes server parameters and status at runtime