* {@link get} : retrieve the value with a key (if any) from cache
* {@link set} : store the value with a key into cache
* {@link add} : store the value only if cache does not have this key
* {@link delete} : delete the value with the specified key from cache
* {@link flush} : delete all values from cache
*
*
* Child classes must implement the following methods:
*
* - {@link getValue}
* - {@link setValue}
* - {@link addValue}
* - {@link deleteValue}
* - {@link flushValues} (optional)
* - {@link serializeValue} (optional)
* - {@link unserializeValue} (optional)
*
*
* Cache also implements ArrayAccess so that it can be used like an array.
*
* @author Qiang Xue
* @since 2.0
*/
abstract class Cache extends ApplicationComponent implements \ArrayAccess
{
/**
* @var string a string prefixed to every cache key so that it is unique. Defaults to null which means
* to use the {@link CApplication::getId() application ID}. If different applications need to access the same
* pool of cached data, the same prefix should be set for each of the applications explicitly.
*/
public $keyPrefix;
/**
* @var boolean whether to hash the cache key for normalization purpose. Defaults to true.
* Setting this property to false makes sure the cache
* key will not be tampered when calling the relevant methods {@link get()}, {@link set()}, {@link add()} and {@link delete()}. This is useful if a Yii
* application as well as an external application need to access the same cache pool (also see description of {@link keyPrefix} regarding this use case).
* However, without normalization you should make sure the affected cache backend does support the structure (charset, length, etc.) of all the provided
* cache keys, otherwise there might be unexpected behavior.
**/
public $hashKey = true;
/**
* @var array|boolean the functions used to serialize and unserialize cached data. Defaults to null, meaning
* using the default PHP `serialize()` and `unserialize()` functions. If you want to use some more efficient
* serializer (e.g. [igbinary](http://pecl.php.net/package/igbinary)), you may configure this property with
* a two-element array. The first element specifies the serialization function, and the second the deserialization
* function. If this property is set false, data will be directly sent to and retrieved from the underlying
* cache component without any serialization or deserialization. You should not turn off serialization if
* you are using [[CacheDependency|cache dependency]], because it relies on data serialization.
*/
public $serializer;
/**
* Initializes the application component.
* This method overrides the parent implementation by setting default cache key prefix.
*/
public function init()
{
parent::init();
if ($this->keyPrefix === null) {
$this->keyPrefix = \Yii::$application->id;
}
}
/**
* @param string $key a key identifying a value to be cached
* @return string a key generated from the provided key which ensures the uniqueness across applications
*/
protected function generateCacheKey($key)
{
return $this->hashKey ? md5($this->keyPrefix . $key) : $this->keyPrefix . $key;
}
/**
* Retrieves a value from cache with a specified key.
* @param string $id a key identifying the cached value
* @return mixed the value stored in cache, false if the value is not in the cache, expired,
* or the dependency associated with the cached data has changed.
*/
public function get($id)
{
$value = $this->getValue($this->generateCacheKey($id));
if ($value === false || $this->serializer === false) {
return $value;
} elseif ($this->serializer === null) {
$value = unserialize($value);
} else {
$value = call_user_func($this->serializer[1], $value);
}
if (is_array($value) && ($value[1] instanceof CacheDependency) || !$value[1]->getHasChanged()) {
return $value[0];
} else {
return false;
}
}
/**
* Retrieves multiple values from cache with the specified keys.
* Some caches (such as memcache, apc) allow retrieving multiple cached values at one time,
* which may improve the performance since it reduces the communication cost.
* In case a cache doesn't support this feature natively, it will be simulated by this method.
* @param array $ids list of keys identifying the cached values
* @return array list of cached values corresponding to the specified keys. The array
* is returned in terms of (key,value) pairs.
* If a value is not cached or expired, the corresponding array value will be false.
*/
public function mget(array $ids)
{
$uids = array();
foreach ($ids as $id) {
$uids[$id] = $this->generateCacheKey($id);
}
$values = $this->getValues($uids);
$results = array();
if ($this->serializer === false) {
foreach ($uids as $id => $uid) {
$results[$id] = isset($values[$uid]) ? $values[$uid] : false;
}
} else {
foreach ($uids as $id => $uid) {
$results[$id] = false;
if (isset($values[$uid])) {
$value = $this->serializer === null ? unserialize($values[$uid]) : call_user_func($this->serializer[1], $values[$uid]);
if (is_array($value) && (!($value[1] instanceof CacheDependency) || !$value[1]->getHasChanged())) {
$results[$id] = $value[0];
}
}
}
}
return $results;
}
/**
* Stores a value identified by a key into cache.
* If the cache already contains such a key, the existing value and
* expiration time will be replaced with the new ones.
*
* @param string $id the key identifying the value to be cached
* @param mixed $value the value to be cached
* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
* @param CacheDependency $dependency dependency of the cached item. If the dependency changes, the item is labeled invalid.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
public function set($id, $value, $expire = 0, $dependency = null)
{
if ($dependency !== null && $this->serializer !== false) {
$dependency->evaluateDependency();
}
if ($this->serializer === null) {
$value = array(serialize($value), $dependency);
} elseif ($this->serializer !== false) {
$value = array(call_user_func($this->serializer[0], $value), $dependency);
}
return $this->setValue($this->generateCacheKey($id), $value, $expire);
}
/**
* Stores a value identified by a key into cache if the cache does not contain this key.
* Nothing will be done if the cache already contains the key.
* @param string $id the key identifying the value to be cached
* @param mixed $value the value to be cached
* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
* @param CacheDependency $dependency dependency of the cached item. If the dependency changes, the item is labeled invalid.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
public function add($id, $value, $expire = 0, $dependency = null)
{
if ($dependency !== null && $this->serializer !== false) {
$dependency->evaluateDependency();
}
if ($this->serializer === null) {
$value = array(serialize($value), $dependency);
} elseif ($this->serializer !== false) {
$value = array(call_user_func($this->serializer[0], $value), $dependency);
}
return $this->addValue($this->generateCacheKey($id), $value, $expire);
}
/**
* Deletes a value with the specified key from cache
* @param string $id the key of the value to be deleted
* @return boolean if no error happens during deletion
*/
public function delete($id)
{
return $this->deleteValue($this->generateCacheKey($id));
}
/**
* Deletes all values from cache.
* Be careful of performing this operation if the cache is shared by multiple applications.
* @return boolean whether the flush operation was successful.
*/
public function flush()
{
return $this->flushValues();
}
/**
* Retrieves a value from cache with a specified key.
* This method should be implemented by child classes to retrieve the data
* from specific cache storage. The uniqueness and dependency are handled
* in {@link get()} already. So only the implementation of data retrieval
* is needed.
* @param string $key a unique key identifying the cached value
* @return string the value stored in cache, false if the value is not in the cache or expired.
*/
protected function getValue($key)
{
return false;
}
/**
* Retrieves multiple values from cache with the specified keys.
* The default implementation simply calls {@link getValue} multiple
* times to retrieve the cached values one by one.
* If the underlying cache storage supports multiget, this method should
* be overridden to exploit that feature.
* @param array $keys a list of keys identifying the cached values
* @return array a list of cached values indexed by the keys
*/
protected function getValues($keys)
{
$results = array();
foreach ($keys as $key) {
$results[$key] = $this->getValue($key);
}
return $results;
}
/**
* Stores a value identified by a key in cache.
* This method should be implemented by child classes to store the data
* in specific cache storage. The uniqueness and dependency are handled
* in {@link set()} already. So only the implementation of data storage
* is needed.
*
* @param string $key the key identifying the value to be cached
* @param string $value the value to be cached
* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
protected function setValue($key, $value, $expire)
{
return true;
}
/**
* Stores a value identified by a key into cache if the cache does not contain this key.
* This method should be implemented by child classes to store the data
* in specific cache storage. The uniqueness and dependency are handled
* in {@link add()} already. So only the implementation of data storage
* is needed.
*
* @param string $key the key identifying the value to be cached
* @param string $value the value to be cached
* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
protected function addValue($key, $value, $expire)
{
return true;
}
/**
* Deletes a value with the specified key from cache
* This method should be implemented by child classes to delete the data from actual cache storage.
* @param string $key the key of the value to be deleted
* @return boolean if no error happens during deletion
*/
protected function deleteValue($key)
{
return true;
}
/**
* Deletes all values from cache.
* Child classes may implement this method to realize the flush operation.
* @return boolean whether the flush operation was successful.
*/
protected function flushValues()
{
return true;
}
/**
* Returns whether there is a cache entry with a specified key.
* This method is required by the interface ArrayAccess.
* @param string $id a key identifying the cached value
* @return boolean
*/
public function offsetExists($id)
{
return $this->get($id) !== false;
}
/**
* Retrieves the value from cache with a specified key.
* This method is required by the interface ArrayAccess.
* @param string $id a key identifying the cached value
* @return mixed the value stored in cache, false if the value is not in the cache or expired.
*/
public function offsetGet($id)
{
return $this->get($id);
}
/**
* Stores the value identified by a key into cache.
* If the cache already contains such a key, the existing value will be
* replaced with the new ones. To add expiration and dependencies, use the set() method.
* This method is required by the interface ArrayAccess.
* @param string $id the key identifying the value to be cached
* @param mixed $value the value to be cached
*/
public function offsetSet($id, $value)
{
$this->set($id, $value);
}
/**
* Deletes the value with the specified key from cache
* This method is required by the interface ArrayAccess.
* @param string $id the key of the value to be deleted
*/
public function offsetUnset($id)
{
$this->delete($id);
}
}