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<sect1 id="zend.cache.backends">
    <title>Zend_Cache Backends</title>
    <para>
        There are two kinds of backends: standard ones and extended ones. Of course, extended backends
        offer more features.
    </para>
    <sect2 id="zend.cache.backends.file">
        <title>Zend_Cache_Backend_File</title>
        <para>
            This (extended) backends stores cache records into files (in a choosen directory).
        </para>
        <para>
            Available options are :
        </para>
        <table id="zend.cache.backends.file.table">
            <title>File Backend Options</title>
            <tgroup cols="4">
                 <thead>
                      <row>
                        <entry>Option</entry>
                        <entry>Data Type</entry>
                        <entry>Default Value</entry>
                        <entry>Description</entry>
                    </row>
                 </thead>
                 <tbody>
                      <row>
                          <entry><code>cache_dir</code></entry>
                          <entry><code>string</code></entry>
                          <entry><code>'/tmp/'</code></entry>
                          <entry>
                              Directory where to store cache files
                          </entry>
                      </row>
                      <row>
                          <entry><code>file_locking</code></entry>
                          <entry><code>boolean</code></entry>
                          <entry><code>true</code></entry>
                          <entry>
                            Enable / disable file_locking : Can avoid cache corruption under
                            bad circumstances but it doesn't help on multithread webservers
                            or on NFS filesystems...
                          </entry>
                      </row>
                      <row>
                          <entry><code>read_control</code></entry>
                          <entry><code>boolean</code></entry>
                          <entry><code>true</code></entry>
                          <entry>
                            Enable / disable read control : if enabled, a control key is
                            embedded in the cache file and this key is compared with the
                            one calculated after the reading.
                          </entry>
                      </row>
                      <row>
                          <entry><code>read_control_type</code></entry>
                          <entry><code>string</code></entry>
                          <entry><code>'crc32'</code></entry>
                          <entry>
                            Type of read control (only if read control is enabled). Available values are :
                            'md5' (best but slowest), 'crc32' (lightly less safe but faster, better choice),
                            'adler32' (new choice, faster than crc32),
                            'strlen' for a length only test (fastest).
                        </entry>
                      </row>
                      <row>
                          <entry><code>hashed_directory_level</code></entry>
                          <entry><code>int</code></entry>
                          <entry><code>0</code></entry>
                          <entry>
                            Hashed directory structure level :     0 means "no hashed directory
                             structure", 1 means "one level of directory", 2 means "two levels"...
                             This option can speed up the cache only when you have many thousands of
                             cache files. Only specific benchs can help you to choose the perfect
                             value for you. Maybe, 1 or 2 is a good start.
                          </entry>
                      </row>
                      <row>
                          <entry><code>hashed_directory_umask</code></entry>
                          <entry><code>int</code></entry>
                          <entry><code>0700</code></entry>
                          <entry>
                              Umask for the hashed directory structure
                        </entry>
                      </row>
                      <row>
                          <entry><code>file_name_prefix</code></entry>
                          <entry><code>string</code></entry>
                          <entry><code>'zend_cache'</code></entry>
                          <entry>
                              prefix for cache files ; be really careful with this option because
                              a too generic value in a system cache dir (like /tmp) can cause
                              disasters when cleaning the cache
                        </entry>
                      </row>
                      <row>
                          <entry><code>cache_file_umask</code></entry>
                          <entry><code>int</code></entry>
                          <entry><code>0700</code></entry>
                          <entry>
                              umask for cache files
                          </entry>
                      </row>
                       <row>
                          <entry><code>metatadatas_array_max_size</code></entry>
                          <entry><code>int</code></entry>
                          <entry><code>100</code></entry>
                          <entry>
                              internal max size for the metadatas array (don't change this value unless you
                              know what you are doing)
                          </entry>
                      </row>
                  </tbody>
              </tgroup>
          </table>
    </sect2>
    <sect2 id="zend.cache.backends.sqlite">
        <title>Zend_Cache_Backend_Sqlite</title>
        <para>
            This (extended) backends stores cache records into a SQLite database.
        </para>
        <para>
            Available options are :
        </para>
        <table id="zend.cache.backends.sqlite.table">
            <title>Sqlite Backend Options</title>
            <tgroup cols="4">
                 <thead>
                      <row>
                           <entry>Option</entry>
                        <entry>Data Type</entry>
                        <entry>Default Value</entry>
                        <entry>Description</entry>
                    </row>
                 </thead>
                 <tbody>
                      <row>
                          <entry><code>cache_db_complete_path (mandatory)</code></entry>
                          <entry><code>string</code></entry>
                          <entry><code>null</code></entry>
                          <entry>
                              The complete path (filename included) of the SQLite database
                          </entry>
                      </row>
                      <row>
                          <entry><code>automatic_vacuum_factor</code></entry>
                          <entry><code>int</code></entry>
                          <entry><code>10</code></entry>
                          <entry>
                              Disable / Tune the automatic vacuum process.
                              The automatic vacuum process defragment the database file (and make it smaller)
                              when a clean() or delete() is called :
                              0 means no automatic vacuum ;
                              1 means systematic vacuum (when delete() or clean() methods are called) ;
                              x (integer) > 1 => automatic vacuum randomly 1 times on x clean() or delete().
                          </entry>
                      </row>
                  </tbody>
              </tgroup>
          </table>
    </sect2>
    <sect2 id="zend.cache.backends.memcached">
        <title>Zend_Cache_Backend_Memcached</title>
        <para>
            This (extended) backends stores cache records into a memcached server. <ulink url="http://www.danga.com/memcached/">memcached</ulink>
            is a high-performance, distributed memory object caching system. To use this backend,
            you need a memcached daemon and <ulink url="http://pecl.php.net/package/memcache">the memcache PECL extension</ulink>.
        </para>
        <para>
            Be careful : with this backend, "tags" are not supported for the moment as
            the "doNotTestCacheValidity=true" argument.
        </para>
        <para>
            Available options are :
        </para>
        <table id="zend.cache.backends.memcached.table">
            <title>Memcached Backend Options</title>
            <tgroup cols="4">
                 <thead>
                      <row>
                        <entry>Option</entry>
                        <entry>Data Type</entry>
                        <entry>Default Value</entry>
                        <entry>Description</entry>
                    </row>
                 </thead>
                 <tbody>
                      <row>
                          <entry><code>servers</code></entry>
                          <entry><code>array</code></entry>
                          <entry>
                            <code>
                              array(array('host' => 'localhost', 'port' => 11211, 'persistent' => true, 'weight' => 1,
                              'timeout' => 5, 'retry_interval' => 15, 'status' => true, 'failure_callback' => '' ))
                            </code>
                          </entry>
                          <entry>
                              An array of memcached servers ; each memcached server is described by an associative array :
                              'host' => (string) : the name of the memcached server,
                              'port' => (int) : the port of the memcached server,
                              'persistent' => (bool) : use or not persistent connections to this memcached server
                              'weight' => (int) :the weight of the memcached server,
                              'timeout' => (int) :the time out of the memcached server,
                              'retry_interval' => (int) :the retry interval of the memcached server,
                              'status' => (bool) :the status of the memcached server,
                              'failure_callback' => (callback) : the failure_callback of the memcached server
                          </entry>
                      </row>
                      <row>
                          <entry><code>compression</code></entry>
                          <entry><code>boolean</code></entry>
                          <entry><code>false</code></entry>
                          <entry>
                             true if you want to use on-the-fly compression
                          </entry>
                      </row>
                      <row>
                          <entry><code>compatibility</code></entry>
                          <entry><code>boolean</code></entry>
                          <entry><code>false</code></entry>
                          <entry>
                             true if you want to use this compatibility mode with old memcache servers/extensions
                          </entry>
                      </row>
                  </tbody>
              </tgroup>
          </table>
    </sect2>
    <sect2 id="zend.cache.backends.apc">
        <title>Zend_Cache_Backend_Apc</title>
        <para>
            This (extended) backends stores cache records in shared memory through
            the <ulink url="http://pecl.php.net/package/APC">APC</ulink> (Alternative PHP Cache) extension
            (which is of course need for using this backend).
        </para>
        <para>
            Be careful : with this backend, "tags" are not supported for the moment as
            the "doNotTestCacheValidity=true" argument.
        </para>
        <para>
            There is no option for this backend.
        </para>
    </sect2>
    <sect2 id="zend.cache.backends.xcache">
        <title>Zend_Cache_Backend_Xcache</title>
        <para>
            This backends stores cache records in shared memory through
            the <ulink url="http://xcache.lighttpd.net/">XCache</ulink> extension
            (which is of course need for using this backend).
        </para>
        <para>
            Be careful : with this backend, "tags" are not supported for the moment as
            the "doNotTestCacheValidity=true" argument.
        </para>
        <para>
            Available options are :
        </para>
        <table id="zend.cache.backends.xcache.table">
            <title>Xcache Backend Options</title>
            <tgroup cols="4">
                 <thead>
                      <row>
                        <entry>Option</entry>
                        <entry>Data Type</entry>
                        <entry>Default Value</entry>
                        <entry>Description</entry>
                    </row>
                 </thead>
                 <tbody>
                      <row>
                          <entry><code>user</code></entry>
                          <entry><code>string</code></entry>
                          <entry><code>null</code></entry>
                          <entry>
                              xcache.admin.user, necessary for the clean() method
                          </entry>
                      </row>
                      <row>
                          <entry><code>password</code></entry>
                          <entry><code>string</code></entry>
                          <entry><code>null</code></entry>
                          <entry>
                              xcache.admin.pass (in clear form, not MD5), necessary for the clean() method
                          </entry>
                      </row>
                  </tbody>
              </tgroup>
          </table>
    </sect2>
    <sect2 id="zend.cache.backends.platform">
        <title>Zend_Cache_Backend_ZendPlatform</title>
        <para>
            This backend uses content caching API of the <ulink url="http://www.zend.com/products/platform">Zend Platform</ulink> product. Naturally, to use this backend you need to have Zend Platform installed.
        </para>
        <para>
    This backend supports tags, but does not support <code>CLEANING_MODE_NOT_MATCHING_TAG</code> cleaning mode.
        </para>
        <para>
            Specify this backend using a word separator -- '-', '.', ' ', or '_'
            -- between the words 'Zend' and 'Platform' when using the
            <classname>Zend_Cache::factory()</classname> method:
        </para>
        <programlisting role="php"><![CDATA[
$cache = Zend_Cache::factory('Core', 'Zend Platform');
]]></programlisting>
        <para>
            There are no options for this backend.
        </para>
    </sect2>
    <sect2 id="zend.cache.backends.twolevels">
        <title>Zend_Cache_Backend_TwoLevels</title>
        <para>
            This (extend) backend is an hybrid one. It stores cache records in two other backends : a fast
            one (but limited) like Apc, Memcache... and a "slow" one like File, Sqlite...
        </para>
        <para>
            This backend will use the priority parameter (given at the frontend level when storing a record)
            and the remaining space in the fast backend to optimize the usage of these two backends.
            FIXME
        </para>
        <para>
            Available options are :
        </para>
        <table id="zend.cache.backends.twolevels.table">
            <title>TwoLevels Backend Options</title>
            <tgroup cols="4">
                 <thead>
                      <row>
                        <entry>Option</entry>
                        <entry>Data Type</entry>
                        <entry>Default Value</entry>
                        <entry>Description</entry>
                    </row>
                 </thead>
                 <tbody>
                      <row>
                          <entry><code>slow_backend</code></entry>
                          <entry><code>string</code></entry>
                          <entry><code>File</code></entry>
                          <entry>
                              the "slow" backend name
                          </entry>
                      </row>
                      <row>
                          <entry><code>fast_backend</code></entry>
                          <entry><code>string</code></entry>
                          <entry><code>Apc</code></entry>
                          <entry>
                              the "fast" backend name
                          </entry>
                      </row>
                      <row>
                          <entry><code>slow_backend_options</code></entry>
                          <entry><code>array</code></entry>
                          <entry><code>array()</code></entry>
                          <entry>
                              the "slow" backend options
                          </entry>
                      </row>
                      <row>
                          <entry><code>fast_backend_options</code></entry>
                          <entry><code>array</code></entry>
                          <entry><code>array()</code></entry>
                          <entry>
                              the "fast" backend options
                          </entry>
                      </row>
                      <row>
                          <entry><code>slow_backend_custom_naming</code></entry>
                          <entry><code>boolean</code></entry>
                          <entry><code>false</code></entry>
                          <entry>
                              if true, the slow_backend argument is used as a complete class name ; if false,
                              the frontend argument is used as the end of "Zend_Cache_Backend_[...]"
                              class name
                          </entry>
                      </row>
                      <row>
                          <entry><code>fast_backend_custom_naming</code></entry>
                          <entry><code>boolean</code></entry>
                          <entry><code>false</code></entry>
                          <entry>
                              if true, the fast_backend argument is used as a complete class name ; if false,
                              the frontend argument is used as the end of "Zend_Cache_Backend_[...]"
                              class name
                          </entry>
                      </row>
                      <row>
                          <entry><code>slow_backend_autoload</code></entry>
                          <entry><code>boolean</code></entry>
                          <entry><code>false</code></entry>
                          <entry>
                              if true, there will no require_once for the slow backend
                              (useful only for custom backends)
                          </entry>
                      </row>
                      <row>
                          <entry><code>fast_backend_autoload</code></entry>
                          <entry><code>boolean</code></entry>
                          <entry><code>false</code></entry>
                          <entry>
                              if true, there will no require_once for the fast backend
                              (useful only for custom backends)
                          </entry>
                      </row>
                      <row>
                          <entry><code>auto_refresh_fast_cache</code></entry>
                          <entry><code>boolean</code></entry>
                          <entry><code>true</code></entry>
                          <entry>
                              if true, auto refresh the fast cache when a cache record is hit
                          </entry>
                      </row>
                      <row>
                          <entry><code>stats_update_factor</code></entry>
                          <entry><code>integer</code></entry>
                          <entry><code>10</code></entry>
                          <entry>
                              disable / tune the computation of the fast backend filling percentage
                              (when saving a record into cache, computation of the fast backend filling percentage
                              randomly 1 times on x cache writes)
                          </entry>
                      </row>
                  </tbody>
              </tgroup>
          </table>
    </sect2>
    <sect2 id="zend.cache.backends.zendserver">
        <title>Zend_Cache_Backend_ZendServer_Disk and Zend_Cache_Backend_ZendServer_ShMem</title>
        <para>
            These backends store cache records using
            <ulink url="http://www.zend.com/en/products/server/downloads-all?zfs=zf_download">Zend Server</ulink> caching functionality.
        </para>
        <para>
             Be careful: with these backends, "tags" are not supported for the moment as the "doNotTestCacheValidity=true" argument.
        </para>
        <para>
             These backend work only withing Zend Server environment for pages requested through HTTP(S) and
             don't work for command line script execution
        </para>
        <para>
            There is no option for this backend.
        </para>
    </sect2>
</sect1>
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