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extended prune documentation, addition of phpfiles adapter docs, rewording of some adapter text for clarity
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‎components/cache/adapters/apcu_adapter.rst

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APCu Cache Adapter
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==================
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This adapter is a high-performance, shared memory cache. It can increase the
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application performance very significantly because the cache contents are
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stored in the shared memory of your server, a component that is much faster than
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others, such as the filesystem.
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This adapter is a high-performance, shared memory cache. It can *significantly* increase
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an application's performance, as its cache contents are stored in shared memory, a component
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appreciably faster than many others, such as the filesystem.
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.. caution::
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**Requirement:** The `APCu extension`_ must be installed and active to use
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this adapter.
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This adapter can be provided an optional namespace string as its first parameter, a
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default cache lifetime as its second parameter, and a version string as its third
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parameter::
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The ApcuAdapter can optionally be provided a namespace, default cache lifetime, and cache
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items version string as constructor arguments::
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use Symfony\Component\Cache\Adapter\ApcuAdapter;
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.. caution::
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It is *not* recommended to use this adapter when performing a large number of
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write and delete operations, as these operations result in fragmentation of the
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APCu memory, resulting in *significantly* degraded performance.
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Use of this adapter is discouraged in write/delete heavy workloads, as these
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operations cause memory fragmentation that results in significantly degraded performance.
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.. tip::
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Note that this adapter's CRUD operations are specific to the PHP SAPI it is running
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under. This means adding a cache item using the CLI will not result in the item
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appearing under FPM. Likewise, deletion of an item using CGI will not result in the
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item being deleted under the CLI.
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This adapter's CRUD operations are specific to the PHP SAPI it is running under. This
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means cache operations (such as additions, deletions, etc) using the CLI will not be
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available under the FPM or CGI SAPIs.
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.. _`APCu extension`: https://pecl.php.net/package/APCu

‎components/cache/adapters/chain_adapter.rst

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single: Cache Pool
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single: Chain Cache
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.. _component-cache-chain-adapter:
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Chain Cache Adapter
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===================
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This adapter allows to combine any number of the other available cache adapters.
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Cache items are fetched from the first adapter which contains them and cache items are
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saved in all the given adapters. This offers a simple way of creating a layered cache.
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This adapter allows combining any number of the other
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:ref:`available cache adapters <component-cache-creating-cache-pools>`. Cache items are
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fetched from the first adapter containing them and cache items are saved to all the
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given adapters. This exposes a simple and efficient method for creating a layeted cache.
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This adapter expects an array of adapters as its first parameter, and optionally a
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maximum cache lifetime as its second parameter::
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The ChainAdapter must be provided an array of adapters and optionally a maximum cache
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lifetime as its constructor arguments::
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use Symfony\Component\Cache\Adapter\ApcuAdapter;
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.. note::
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When an item is not found in the first adapter but is found in the next ones, this
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adapter ensures that the fetched item is saved in all the adapters where it was
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adapter ensures that the fetched item is saved to all the adapters where it was
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previously missing.
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The following example shows how to create a chain adapter instance using the fastest and
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new FilesystemAdapter(),
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));
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When calling this adapter's :method:`Symfony\\Component\\Cache\\ChainAdapter::prune` method,
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the call is deligated to all its compatibe cache adapters. It is safe to mix both adapters
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that *do* and do *not* implement :class:`Symfony\\Component\\Cache\\PruneableInterface`, as
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incompatible adapters are silently ignored::
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use Symfony\Component\Cache\Adapter\ApcuAdapter;
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use Symfony\Component\Cache\Adapter\ChainAdapter;
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use Symfony\Component\Cache\Adapter\FilesystemAdapter;
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$cache = new ChainAdapter(array(
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new ApcuAdapter(), // does NOT implement PruneableInterface
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new FilesystemAdapter(), // DOES implement PruneableInterface
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));
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// prune will proxy the call to FilesystemAdapter while silently skipping ApcuAdapter
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$cache->prune();
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.. note::
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This adapter implements :class:`Symfony\\Component\\Cache\\PruneableInterface`, allowing
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for manual :ref:`pruning of expired cache entries <component-cache-cache-pool-prune>` by
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calling it's ``prune()`` method.
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Since Symfony 3.4, this adapter implements :class:`Symfony\\Component\\Cache\\PruneableInterface`,
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allowing for manual :ref:`pruning of expired cache entries <component-cache-cache-pool-prune>` by
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calling its ``prune()`` method.

‎components/cache/adapters/filesystem_adapter.rst

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single: Cache Pool
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single: Filesystem Cache
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.. _component-cache-filesystem-adapter:
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Filesystem Cache Adapter
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========================
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This adapter is useful when you want to improve the application performance but
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can't install tools like APCu or Redis on the server. This adapter stores the
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contents as regular files in a set of directories on the local file system.
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This adapter offers improved application performance for those who cannot install
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tools like :ref:`APCu <apcu-adapter>` or :ref:`Redis <redis-adapter>` in their
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environment. It stores the cache item expiration and content as regular files in
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a collection of directories on a locally mounted filesystem.
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.. tip::
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The performance of this adapter can be greatly increased by utalizing a
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temporary, in-memory filesystem, such as `tmpfs`_ on Linux, or one of the
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many other `RAM disk solutions`_ available.
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This adapter can optionally be provided a namespace, default cache lifetime, and
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directory path, as its first, second, and third parameters::
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The FilesystemAdapter can optionally be provided a namespace, default cache lifetime,
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and cache root path as constructor parameters::
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use Symfony\Component\Cache\Adapter\FilesystemAdapter;
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$directory = null
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);
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.. tip::
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.. caution::
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This adapter is generally the *slowest* due to the overhead of file IO. If throughput is paramount,
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the in-memory adapters (such as :ref:`APCu <apcu-adapter>`, :ref:`Memcached <memcached-adapter>`,
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and :ref:`Redis <redis-adapter>`) or the database adapters (such as
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:ref:`Doctrine <doctrine-adapter>` and :ref:`PDO & Doctrine <pdo-doctrine-adapter>`) are recommended.
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The overhead of filesystem IO often makes this adapter one of the *slower* choices. If throughput is
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paramount, the in-memory adapters (:ref:`Apcu <apcu-adapter>`, :ref:`Memcached <memcached-adapter>`,
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and :ref:`Redis <redis-adapter>`) or the database adapters (:ref:`Doctrine <doctrine-adapter>` and
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:ref:`PDO <pdo-doctrine-adapter>`) are recommended.
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.. note::
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This adapter implements :class:`Symfony\\Component\\Cache\\PruneableInterface`, allowing
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for manual :ref:`pruning of expired cache entries <component-cache-cache-pool-prune>` by
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calling it's ``prune()`` method.
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Since Symfony 3.4, this adapter implements :class:`Symfony\\Component\\Cache\\PruneableInterface`,
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enabling manual :ref:`pruning of expired cache items <component-cache-cache-pool-prune>` by
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calling its ``prune()`` method.
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.. _`tmpfs`: https://wiki.archlinux.org/index.php/tmpfs
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.. _`RAM disk solutions`: https://en.wikipedia.org/wiki/List_of_RAM_drive_software

‎components/cache/adapters/pdo_doctrine_dbal_adapter.rst

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.. note::
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This adapter implements :class:`Symfony\\Component\\Cache\\PruneableInterface`, allowing
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for manual :ref:`pruning of expired cache entries <component-cache-cache-pool-prune>` by
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calling it's ``prune()`` method.
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Since Symfony 3.4, this adapter implements :class:`Symfony\\Component\\Cache\\PruneableInterface`,
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allowing for manual :ref:`pruning of expired cache entries <component-cache-cache-pool-prune>` by
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calling its ``prune()`` method.
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.. _`PDO`: http://php.net/manual/en/class.pdo.php
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.. _`Doctrine DBAL Connection`: https://github.com/doctrine/dbal/blob/master/lib/Doctrine/DBAL/Connection.php

‎components/cache/adapters/php_array_cache_adapter.rst

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that is optimized and preloaded into OPcache memory storage::
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use Symfony\Component\Cache\Adapter\PhpArrayAdapter;
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use Symfony\Component\Cache\Adapter\PhpFilesAdapter;
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use Symfony\Component\Cache\Adapter\FilesystemAdapter;
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// somehow, decide it's time to warm up the cache! F438
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if ($needsWarmup) {

‎components/cache/adapters/php_files_adapter.rst

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.. index::
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single: Cache Pool
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single: PHP Files Cache
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.. _component-cache-files-adapter:
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Php Files Cache Adapter
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=======================
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Similarly to :ref:`Filesystem Adapter <component-cache-filesystem-adapter>`, this cache
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implementation writes cache entries out to disk, but unlike the Filesystem cache adapter,
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the PHP Files cache adapter writes and reads back these cache files *as native PHP code*.
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For example, caching the value ``array('my', 'cached', 'array')`` will write out a cache
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file similar to the following::
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<?php return array(
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// the cache item expiration
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0 => 9223372036854775807,
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// the cache item contents
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1 => array (
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0 => 'my',
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1 => 'cached',
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2 => 'array',
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),
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);
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.. note::
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As cache items are included and parsed as native PHP code and due to the way `OPcache`_
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handles file includes, this adapter has the potential to be much faster than other
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filesystem-based caches.
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The PhpFilesAdapter can optionally be provided a namespace, default cache lifetime, and cache
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directory path as constructor arguments::
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use Symfony\Component\Cache\Adapter\PhpFilesAdapter;
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$cache = new PhpFilesAdapter(
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// a string used as the subdirectory of the root cache directory, where cache
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// items will be stored
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$namespace = '',
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// the default lifetime (in seconds) for cache items that do not define their
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// own lifetime, with a value 0 causing items to be stored indefinitely (i.e.
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// until the files are deleted)
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$defaultLifetime = 0,
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// the main cache directory (the application needs read-write permissions on it)
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// if none is specified, a directory is created inside the system temporary directory
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$directory = null
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);
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.. note::
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Since Symfony 3.4, this adapter implements :class:`Symfony\\Component\\Cache\\PruneableInterface`,
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allowing for manual :ref:`pruning of expired cache entries <component-cache-cache-pool-prune>` by
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calling its ``prune()`` method.
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.. _`OPcache`: http://php.net/manual/en/book.opcache.php

‎components/cache/cache_pools.rst

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can keep using the same cache pool even if the underlying cache mechanism
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changes from a file system based cache to a Redis or database based cache.
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.. _component-cache-creating-cache-pools:
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Creating Cache Pools
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--------------------
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.. versionadded:: 3.4
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Pruning functionality was introduced in Symfony 3.4.
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Some cache pools do not include an automated mechanism for pruning expired cache
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items. For example, :class:`Symfony\\Component\\Cache\\Adapter\\FilesystemAdapter`
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does not remove expired items until one is explicitly requested and determined to
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be expired, for example, via a call to :method:`Psr\\Cache\\CacheItemPoolInterface::getItem`.
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This may result in many stale cache entries persisting well past their expiration,
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causing a build up that can result in a sizable consumption of wasted disk or memory
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space.
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This concern has been resolved through the introduction of
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:class:`Symfony\\Component\\Cache\\PruneableInterface`, an interface defining a
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singular ``prune()`` method. Relevant cache adapters, those that allow expired cache
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entries to proliferate, now implement ``PruneableInterface``, allowing for these
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excess cache entries to be manually removed::
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Cache adapter pruning functionality was introduced in Symfony 3.4.
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Some cache pools do not include an automated mechanism for pruning expired cache items.
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For example, the :ref:`FilesystemAdaper <component-cache-filesystem-adapter>` cache
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does not remove expired cache items *until an item is explicitly requested and determined to
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be expired*, for example, via a call to :method:`Psr\\Cache\\CacheItemPoolInterface::getItem`.
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Under certain workloads, this can cause stale cache entries to persist well past their
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expiration, resulting in a sizable consumption of wasted disk or memory space from
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excess, expired cache items.
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This shortcomming has been solved through the introduction of
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:class:`Symfony\\Component\\Cache\\PruneableInterface`, which defines the abstract method
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:method:`Symfony\\Component\\Cache\\PruneableInterface::prune`. The
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:ref:`ChainAdapter <component-cache-chain-adapter>`,
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:ref:`FilesystemAdaper <component-cache-filesystem-adapter>`,
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:ref:`PdoAdapter <pdo-doctrine-adapter>`, and
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:ref:`PhpFilesAdapter <component-cache-files-adapter>` all implement this new interface,
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allowing manual removal of stale cache items::
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use Symfony\Component\Cache\Adapter\FilesystemAdapter;
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$cache = new FilesystemAdapter('app.cache');
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// ... do some set and get operations
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$cache->prune();
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The :ref:`ChainAdapter <component-cache-chain-adapter>` implementation does not directly
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contain any pruning logic itself. Instead, when calling the chain adapter's
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:method:`Symfony\\Component\\Cache\\ChainAdapter::prune` method, the call is deligated to all
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its compatibe cache adapters (and those that do not implement ``PruneableInterface`` are
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silently ignored)::
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use Symfony\Component\Cache\Adapter\ApcuAdapter;
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use Syfmony\Component\Cache\Adapter\ChainAdapter;
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use Syfmony\Component\Cache\Adapter\FilesystemAdapter;
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use Syfmony\Component\Cache\Adapter\PdoAdapter;
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use Syfmony\Component\Cache\Adapter\PhpFilesAdapter;
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$cache = new ChainAdapter(array(
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new ApcuAdapter(), // does NOT implement PruneableInterface
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new FilesystemAdapter(), // DOES implement PruneableInterface
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new PdoAdapter(), // DOES implement PruneableInterface
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new PhpFilesAdapter(), // DOES implement PruneableInterface
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// ...
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));
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// prune will proxy the call to PdoAdapter, FilesystemAdapter and PhpFilesAdapter,
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// while silently skipping ApcuAdapter
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$cache->prune();

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