# Caching Driver

CodeIgniter features wrappers around some of the most popular forms of fast and dynamic caching. All but file-based caching require specific server requirements, and a Fatal Exception will be thrown if server requirements are not met.

## Example Usage

The following example will load the cache driver, specify APC as the driver to use, and fall back to file-based caching if APC is not available in the hosting environment.

    $this->load->driver('cache', array('adapter' => 'apc', 'backup' => 'file'));

    if ( ! $foo = $this->cache->get('foo'))
    {
            echo 'Saving to the cache!<br />';
            $foo = 'foobarbaz!';

            // Save into the cache for 5 minutes
            $this->cache->save('foo', $foo, 300);
    }

    echo $foo;

You can also prefix cache item names via the key_prefix setting, which is useful to avoid collisions when you’re running multiple applications on the same environment.

    $this->load->driver('cache',
            array('adapter' => 'apc', 'backup' => 'file', 'key_prefix' => 'my_')
    );

    $this->cache->get('foo'); // Will get the cache entry named 'my_foo'

## Class Reference

class CI_Cache
  is_supported($driver)
    Parameters:

      - $driver (`string`) – the name of the caching driver

    Returns:

      TRUE if supported, FALSE if not

    Return type:

      `bool`

    This method is automatically called when accessing drivers via `$this->cache->get()`. However, if the individual drivers are used, make sure to call this method to ensure the driver is supported in the hosting environment.

        if ($this->cache->apc->is_supported())
        {
                if ($data = $this->cache->apc->get('my_cache'))
                {
                        // do things.
                }
        }

  get($id)
    Parameters:

      - $id (`string`) – Cache item name

    Returns:

      Item value or FALSE if not found

    Return type:

      `mixed`

    This method will attempt to fetch an item from the cache store. If the item does not exist, the method will return FALSE.

        $foo = $this->cache->get('my_cached_item');

  save($id, $data[, $ttl = 60[, $raw = FALSE]])
    Parameters:

      - $id (`string`) – Cache item name

      - $data (`mixed`) – the data to save

      - $ttl (`int`) – Time To Live, in seconds (default 60)

      - $raw (`bool`) – Whether to store the raw value

    Returns:

      TRUE on success, FALSE on failure

    Return type:

      `string`

    This method will save an item to the cache store. If saving fails, the method will return FALSE.

        $this->cache->save('cache_item_id', 'data_to_cache');

    Note

    The `$raw` parameter is only utilized by APC and Memcache, in order to allow usage of `increment()` and `decrement()`.

  delete($id)
    Parameters:

      - $id (`string`) – name of cached item

    Returns:

      TRUE on success, FALSE on failure

    Return type:

      `bool`

    This method will delete a specific item from the cache store. If item deletion fails, the method will return FALSE.

        $this->cache->delete('cache_item_id');

  increment($id[, $offset = 1])
    Parameters:

      - $id (`string`) – Cache ID

      - $offset (`int`) – Step/value to add

    Returns:

      New value on success, FALSE on failure

    Return type:

      `mixed`

    Performs atomic incrementation of a raw stored value.

        // 'iterator' has a value of 2

        $this->cache->increment('iterator'); // 'iterator' is now 3

        $this->cache->increment('iterator', 3); // 'iterator' is now 6

  decrement($id[, $offset = 1])
    Parameters:

      - $id (`string`) – Cache ID

      - $offset (`int`) – Step/value to reduce by

    Returns:

      New value on success, FALSE on failure

    Return type:

      `mixed`

    Performs atomic decrementation of a raw stored value.

        // 'iterator' has a value of 6

        $this->cache->decrement('iterator'); // 'iterator' is now 5

        $this->cache->decrement('iterator', 2); // 'iterator' is now 3

  clean()
    Returns:

      TRUE on success, FALSE on failure

    Return type:

      `bool`

    This method will ‘clean’ the entire cache. If the deletion of the cache files fails, the method will return FALSE.

        $this->cache->clean();

  cache_info()
    Returns:

      Information on the entire cache database

    Return type:

      `mixed`

    This method will return information on the entire cache.

        var_dump($this->cache->cache_info());

    Note

    The information returned and the structure of the data is dependent on which adapter is being used.

  get_metadata($id)
    Parameters:

      - $id (`string`) – Cache item name

    Returns:

      Metadata for the cached item

    Return type:

      `mixed`

    This method will return detailed information on a specific item in the cache.

        var_dump($this->cache->get_metadata('my_cached_item'));

    Note

    The information returned and the structure of the data is dependent on which adapter is being used.

## Drivers

### Alternative PHP Cache (APC) Caching

All of the methods listed above can be accessed without passing a specific adapter to the driver loader as follows:

    $this->load->driver('cache');
    $this->cache->apc->save('foo', 'bar', 10);

For more information on APC, please see http://php.net/apc.

### File-based Caching

Unlike caching from the Output Class, the driver file-based caching allows for pieces of view files to be cached. Use this with care, and make sure to benchmark your application, as a point can come where disk I/O will negate positive gains by caching.

All of the methods listed above can be accessed without passing a specific adapter to the driver loader as follows:

    $this->load->driver('cache');
    $this->cache->file->save('foo', 'bar', 10);

### Memcached Caching

Multiple Memcached servers can be specified in the memcached.php configuration file, located in the _application/config/* directory.

All of the methods listed above can be accessed without passing a specific adapter to the driver loader as follows:

    $this->load->driver('cache');
    $this->cache->memcached->save('foo', 'bar', 10);

For more information on Memcached, please see http://php.net/memcached.

### WinCache Caching

Under Windows, you can also utilize the WinCache driver.

All of the methods listed above can be accessed without passing a specific adapter to the driver loader as follows:

    $this->load->driver('cache');
    $this->cache->wincache->save('foo', 'bar', 10);

For more information on WinCache, please see http://php.net/wincache.

### Redis Caching

Redis is an in-memory key-value store which can operate in LRU cache mode. To use it, you need Redis server and phpredis PHP extension.

Config options to connect to redis server must be stored in the application/config/redis.php file. Available options are:

    $config['socket_type'] = 'tcp'; //`tcp` or `unix`
    $config['socket'] = '/var/run/redis.sock'; // in case of `unix` socket type
    $config['host'] = '127.0.0.1';
    $config['password'] = NULL;
    $config['port'] = 6379;
    $config['timeout'] = 0;

All of the methods listed above can be accessed without passing a specific adapter to the driver loader as follows:

    $this->load->driver('cache');
    $this->cache->redis->save('foo', 'bar', 10);

For more information on Redis, please see http://redis.io.

### Dummy Cache

This is a caching backend that will always ‘miss.’ It stores no data, but lets you keep your caching code in place in environments that don’t support your chosen cache.