Horde_Cache 2.3.0.

Changes have been made in Git (master):

commit 923c200e1165144f9d1bb4a1e39073bab4181dd8
Author: Michael M Slusarz <slusarz@horde.org>
Date:   Sun Oct 6 22:53:29 2013 -0600

     [mms] Fix key expiration for APC, Eaccelerator, and Xcache (Bug #12735).

  framework/Cache/lib/Horde/Cache/Storage/Apc.php    |    1 -
  .../Cache/lib/Horde/Cache/Storage/Eaccelerator.php |    1 -
  framework/Cache/lib/Horde/Cache/Storage/Xcache.php |    3 +--
  framework/Cache/package.xml                        |    2 ++
  4 files changed, 3 insertions(+), 4 deletions(-)

http://git.horde.org/horde-git/-/commit/923c200e1165144f9d1bb4a1e39073bab4181dd8

I reconsidered my patch...

_setExpire is protected and used only in the Xcache Module for get() 
and exists(). Both add the prefix before calling _setExpire.

Removing the second addition of the prefix in _setExpire() seems more 
reasonable.

--------
--- Xcache.php.orig        2013-10-05 01:44:50.000000000 +0200
+++ Xcache.php        2013-10-05 01:55:58.000000000 +0200
@@ -97,7 +97,6 @@
              // don't expire
              return;
          }
-        $key = $this->_params['prefix'] . $key;
          $expire = xcache_get($key . '_expire');

          // set prune period
--------

If eg. kronolith freebusy fb.php uses
$fb = $cache->get($key, 360);
in case of Xcache get() adds the prefix to $key and calls 
_setExpire(). But there the prefix is added again.

I think this will work as expected and similar to other caching modules
--------------
--- Xcache.php.orig        2013-10-05 01:44:50.000000000 +0200
+++ Xcache.php        2013-10-05 01:45:58.000000000 +0200
@@ -40,8 +40,10 @@
       */
      public function get($key, $lifetime = 0)
      {
-        $key = $this->_params['prefix'] . $key;
+        /* prefix is added in _setExpire, too */
          $this->_setExpire($key, $lifetime);
+        /* add it after calling _setExpire */
+        $key = $this->_params['prefix'] . $key;
          $result = xcache_get($key);

          return empty($result)
---------