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.

Table 170. 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 Appendix I, 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

Table 171. 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 1305. 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.

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<?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 1306. Using memcache session handler

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<?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

Code Examples / Notes » ref.memcache

Here is a simple memcached aggregator class which distributes the cache among multiple cache servers. If a server fails, the load is redistributed automatically. It uses persistent connections. The constructor takes an array of arrays, with each inner array representing a server, with a 'server' (string) attribute that is the IP addres or host name of the memcached server, and a 'port' (int) attribute that is the port number on which memcached is running on the server. All of the existing memcached API functions are implemented except getStats() and getVersion(), which are server-specific. <?php class MemcachedAggregator { var $connections; public function __construct($servers) { // Attempt to establish/retrieve persistent connections to all servers. // If any of them fail, they just don't get put into our list of active // connections. $this->connections = array(); for ($i = 0, $n = count($servers); $i < $n; $i++) { $server = $servers[$i]; $con = memcache_pconnect($server['host'], $server['port']); if (!($con == false)) { $this->connections[] = $con; } } } private function _getConForKey($key) { $hashCode = 0; for ($i = 0, $len = strlen($key); $i < $len; $i++) { $hashCode = (int)(($hashCode*33)+ord($key[$i])) & 0x7fffffff; } if (($ns = count($this->connections)) > 0) { return $this->connections[$hashCode%$ns]; } return false; } public function debug($on_off) { $result = false; for ($i = 0; $i < count($connections); $i++) { if ($this->connections[$i]->debug($on_off)) $result = true; } return $result; } public function flush() { $result = false; for ($i = 0; $i < count($connections); $i++) { if ($this->connections[$i]->flush()) $result = true; } return $result; } /// The following are not implemented: ///getStats() ///getVersion() public function get($key) { if (is_array($key)) { $dest = array(); foreach ($key as $subkey) { $val = get($subkey); if (!($val === false)) $dest[$subkey] = $val; } return $dest; } else { return $this->_getConForKey($key)->get($key); } } public function set($key, $var, $compress=0, $expire=0) { return $this->_getConForKey($key)->set($key, $var, $compress, $expire); } public function add($key, $var, $compress=0, $expire=0) { return $this->_getConForKey($key)->add($key, $var, $compress, $expire); } public function replace($key, $var, $compress=0, $expire=0) { return $this->_getConForKey($key)->replace ($key, $var, $compress, $expire); } public function delete($key, $timeout=0) { return $this->_getConForKey($key)->delete($key, $timeout); } public function increment($key, $value=1) { return $this->_getConForKey($key)->increment($key, $value); } public function decrement($key, $value=1) { return $this->_getConForKey($key)->decrement($key, $value); } } ?>

Here is a PHP4 backport of the above MemcacheAggregator class: <?php class MemcachedAggregator { var $connections; var $_servers; function MemcachedAggregator($servers) { $this->_servers = $servers; // Attempt to establish/retrieve persistent connections to all servers. // If any of them fail, they just don't get put into our list of active // connections. $this->connections = array(); for ($i = 0, $n = count($servers); $i < $n; $i++) { $server = $servers[$i]; $con = memcache_connect($server['host']); //memcache_debug(1); //$memcache = &new Memcache; //$con = $memcache->connect($server['host']); if (!($con == false)) { $this->connections[] = &$con; } } } function _getConForKey($key) { $hashCode = 0; for ($i = 0, $len = strlen($key); $i < $len; $i++) { $hashCode = (int)(($hashCode*33)+ord($key[$i])) & 0x7fffffff; } if (($ns = count($this->connections)) > 0) { return $this->connections[$hashCode%$ns]; //return $this->connections[0]; } return false; } function debug($on_off) { $result = false; for ($i = 0; $i < count($this->connections); $i++) { if ($this->connections[$i]->debug($on_off)) $result = true; } return $result; } function flush() { $result = false; for ($i = 0; $i < count($this->connections); $i++) { if ($this->connections[$i]->flush()) $result = true; } return $result; } /// The following are not implemented: ///getStats() ///getVersion() function get($key) { if (is_array($key)) { $dest = array(); foreach ($key as $subkey) { $val = get($subkey); if (!($val === false)) $dest[$subkey] = $val; } return $dest; } else { $conn = &$this->_getConForKey($key); return $conn->get($key); } } function set($key, $var, $compress=0, $expire=0) { $conn = &$this->_getConForKey($key); return $conn->set($key, $var, $compress, $expire); } function add($key, $var, $compress=0, $expire=0) { $conn = &$this->_getConForKey($key); return $conn->add($key, $var, $compress, $expire); } function replace($key, $var, $compress=0, $expire=0) { $conn = &$this->_getConForKey($key); return $conn->replace($key, $var, $compress, $expire); } function delete($key, $timeout=0) { $conn = &$this->_getConForKey($key); return $conn->delete($key, $timeout); } function increment($key, $value=1) { $conn = &$this->_getConForKey($key); return $conn->increment($key, $value); } function decrement($key, $value=1) { $conn = &$this->_getConForKey($key); return $conn->decrement($key, $value); } function showStats($server=null) { $stats_out = ''; if($server == null) { $i=0; foreach($this->connections as $conn) { $server = $this->_servers[$i]; $stats_array = memcache_get_stats($conn); $stats_out .= "Server: ".$server['host'].": "; foreach($stats_array as $key => $val) { $stats_out .= "$key => $val "; } $i++; } } return $stats_out; } } ?>

Memcache Functions

Introduction

Requirements

Installation

Runtime Configuration

Table 170. Memcache Configuration Options

Resource Types

Predefined Constants

Table 171. Memcache Constants

Examples

Example 1305. memcache extension overview example

Example 1306. Using memcache session handler

Code Examples / Notes » ref.memcache

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