Memcache

Introduction
Installing/Configuring
Predefined Constants
Examples
- Basic usage
Memcache — The Memcache class
- 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::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
Memcache Functions
- memcache_debug — Turn debug output on/off

User Contributed Notes

gabriel dot maybrun at demandmedia dot com

1 year ago


GOTCHA: Recently I was tasked with moving from PECL memcache to PECL memcached and ran into a major problem -- memcache and memcached serialize data differently, meaning that data written with one library can't necessarily be read with the other library.

For example, If you write an object or an array with memcache, it's interpreted as an integer by memcached.  If you write it with memcached, it's interpreted as a string by memcache.

tl;dr - You can't safely switch between memcache and memcached without a either a cache flush or isolated cache environments.

<?php
$memcache = new Memcache;
$memcacheD = new Memcached;
$memcache->addServer($host);
$memcacheD->addServers($servers);

$checks = array(
    123,
    4542.32,
    'a string',
    true,
    array(123, 'string'),
    (object)array('key1' => 'value1'),
);
foreach ($checks as $i => $value) {
    print "Checking WRITE with Memcache\n";
    $key = 'cachetest' . $i;
    $memcache->set($key, $value);
    usleep(100);
    $val = $memcache->get($key);
    $valD = $memcacheD->get($key);
    if ($val !== $valD) {
        print "Not compatible!";
        var_dump(compact('val', 'valD'));
    }

    print "Checking WRITE with MemcacheD\n";
    $key = 'cachetest' . $i;
    $memcacheD->set($key, $value);
    usleep(100);
    $val = $memcache->get($key);
    $valD = $memcacheD->get($key);
    if ($val !== $valD) {
        print "Not compatible!";
        var_dump(compact('val', 'valD'));
    }
}

Anonymous

1 year ago


I ran Gabriel's test above and had different results. I did find differences in the objects. For instance:
  'val' => string(7) "4542.32"
  'valD' => double(4542.32)

But, I think this could be resolved. Fairly easily.

 The main issue with the test was that one port is used. I ran another instance of memcached on a different port and changed the code slightly.  I used this code and had better success:

$servers = array(array('localserv', 11212));
$memcache = new Memcache;
$memcacheD = new Memcached;
$memcache->addServer('localserv', 11211);
$memcacheD->addServers($servers);
$memcacheD->setOption(Memcached::OPT_BINARY_PROTOCOL, true);

$checks = array(
    123,
    4542.32,
    'a string',
    true,
    array(123, 'string'),
    (object)array('key1' => 'value1'),
);
foreach ($checks as $i => $value) {
    print "Checking WRITE with Memcache\n";
    $key = 'cachetest' . $i;
    $memcache->set($key, $value);
    usleep(100);
    $val = $memcache->get($key);
    $valD = $memcacheD->get($key);
    if ($val !== $valD) {
        print "Not compatible!";
        var_dump(compact('val', 'valD'));
    } else {
        print "WAS COMPAT\n";
    }

    print "Checking WRITE with MemcacheD\n";
    $key = 'cachetest' . $i;
    $memcacheD->set($key, $value);
    usleep(100);
    $val = $memcache->get($key);
    $valD = $memcacheD->get($key);
    if ($val !== $valD) {
        print "Not compatible!";
        var_dump(compact('val', 'valD'));
    } else {
        print "WAS COMPAT\n";
    }
}