LXXII. Memcache Functions


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.

This module doesn't have native support of multiple servers, but you still can implement it yourself in your application. Establish several memcached connections, set priority level for each server etc.

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


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.


PECL 扩展未绑定于 PHP 中。 进一步信息例如新版本,下载,源程序,维护者信息以及更新日志可以在此找到: 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。


表格 1. MemCache Constants

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


本扩展模块在 php.ini 中未定义任何配置选项。


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


例子 1. memcache extension overview example


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

$version = $memcache->getVersion();
"Server's version: ".$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");
"Store data in the cache (data will expire in 10 seconds)<br/>\n";

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



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.

Memcache::add -- Add an item to the server
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::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

add a note add a note User Contributed Notes
ed at me3inc dot com
27-Oct-2006 05:47
Re. Installing the memcache extension:

I had all kinds of troubles getting it hooked up, because in all of the instructions I read I never got the last, most important step - you must have a php.ini and have in it "extension=memcache.so."

So, the steps:
First - ./configure with --enable-memcache. This should show in your phpinfo() at the top (even though nothing of the memcache extension works yet).

either pecl install memcache
download the source
tar -xzvf [thesourcetarball]
make install

Finally: Add extension=memcache.so to your php.ini. (If you don't have one, it should go in the root of where php is called ie., /usr/local/lib)

Call phpinfo() and you should see a memcache section.
iliya at pisem dot net
20-Jan-2006 04:35
one more "intelligent" cache aggregator:
https://svn.shadanakar.org/onPHP/ trunk/core/Cache/AggregateCache.class.php
can be used with several cache connectors - memcached, filesystem, etc.
(remove whitespace manually)
Gregor J. Rothfuss
22-Nov-2005 01:18
The next version will have failover. It's been committed three weeks ago. Usage notes here: http://www.codecomments.com/archive367-2005-10-659421.html
15-Sep-2005 04:19
An improvement to the above:

The above class will cause an error if all cache servers are down.  The preferred behavior is to just have a cache miss (or take no action in the case of write operations) and return false, so the app can run in non-cached mode if all cache servers are down.

To make this happen, simply change the connection usage to look something like this in each affected function.  This code is for the get() function:

       $con = $this->_getConForKey($key);
       if ($con === false) return false;
       return $con->get($key);

Similarly, the affected code in the set() function would look like this:
   $con = $this->_getConForKey($key);
   if ($con === false) return false;
   return $con->set($key, $var, $compress, $expire);

Modify each function accordingly, and if all of your cache servers are down, you can still function (although more slowly due to the 100% cache miss rate).
15-Sep-2005 01:20
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.

class MemcachedAggregator {

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) {

public function debug($on_off) {
$result = false;
   for (
$i = 0; $i < count($connections); $i++) {
       if (
$this->connections[$i]->debug($on_off)) $result = true;

public function flush() {
$result = false;
   for (
$i = 0; $i < count($connections); $i++) {
       if (
$this->connections[$i]->flush()) $result = true;

/// The following are not implemented:

public function get($key) {
   if (
is_array($key)) {
$dest = array();
       foreach (
$key as $subkey) {
$val = get($subkey);
       if (!(
$val === false)) $dest[$subkey] = $val;
   } else {

public function set($key, $var, $compress=0, $expire=0) {
$this->_getConForKey($key)->set($key, $var, $compress, $expire);

public function add($key, $var, $compress=0, $expire=0) {
$this->_getConForKey($key)->add($key, $var, $compress, $expire);

public function replace($key, $var, $compress=0, $expire=0) {
($key, $var, $compress, $expire);

public function delete($key, $timeout=0) {
$this->_getConForKey($key)->delete($key, $timeout);

public function increment($key, $value=1) {
$this->_getConForKey($key)->increment($key, $value);

public function decrement($key, $value=1) {
$this->_getConForKey($key)->decrement($key, $value);