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使用缓存提高性能（Improving Performance with Cache）¶Phalcon provides the Phalcon\Cache class allowing faster access to frequently used or already processed data. Phalcon\Cache is written in C, achieving higher performance and reducing the overhead when getting items from the backends. This class uses an internal structure of frontend and backend components. Front-end components act as input sources or interfaces, while backend components offer storage options to the class. 什么情况下使用缓存？（When to implement cache?）¶Although this component is very fast, implementing it in cases that are not needed could lead to a loss of performance rather than gain. We recommend you check this cases before using a cache:
缓存行为（Caching Behavior）¶The caching process is divided into 2 parts:
缓存输出片段（Caching Output Fragments）¶An output fragment is a piece of HTML or text that is cached as is and returned as is. The output is automatically captured from the ob_* functions or the PHP output so that it can be saved in the cache. The following example demonstrates such usage. It receives the output generated by PHP and stores it into a file. The contents of the file are refreshed every 172800 seconds (2 days). The implementation of this caching mechanism allows us to gain performance by not executing the helper Phalcon\Tag::linkTo call whenever this piece of code is called. <?php
//Create an Output frontend. Cache the files for 2 days
$frontCache = new Phalcon\Cache\Frontend\Output(array(
"lifetime" => 172800
));
// Create the component that will cache from the "Output" to a "File" backend
// Set the cache file directory - it's important to keep the "/" at the end of
// the value for the folder
$cache = new Phalcon\Cache\Backend\File($frontCache, array(
"cacheDir" => "../app/cache/"
));
// Get/Set the cache file to ../app/cache/my-cache.html
$content = $cache->start("my-cache.html");
// If $content is null then the content will be generated for the cache
if ($content === null) {
//Print date and time
echo date("r");
//Generate a link to the sign-up action
echo Phalcon\Tag::linkTo(
array(
"user/signup",
"Sign Up",
"class" => "signup-button"
)
);
// Store the output into the cache file
$cache->save();
} else {
// Echo the cached output
echo $content;
}
NOTE In the example above, our code remains the same, echoing output to the user as it has been doing before. Our cache component transparently captures that output and stores it in the cache file (when the cache is generated) or it sends it back to the user pre-compiled from a previous call, thus avoiding expensive operations. 缓存任意数据（Caching Arbitrary Data）¶Caching just data is equally important for your application. Caching can reduce database load by reusing commonly used (but not updated) data, thus speeding up your application. 文件后端存储器例子（File Backend Example）¶One of the caching adapters is ‘File’. The only key area for this adapter is the location of where the cache files will be stored. This is controlled by the cacheDir option which must have a backslash at the end of it. <?php
// Cache the files for 2 days using a Data frontend
$frontCache = new Phalcon\Cache\Frontend\Data(array(
"lifetime" => 172800
));
// Create the component that will cache "Data" to a "File" backend
// Set the cache file directory - important to keep the "/" at the end of
// of the value for the folder
$cache = new Phalcon\Cache\Backend\File($frontCache, array(
"cacheDir" => "../app/cache/"
));
// Try to get cached records
$cacheKey = 'robots_order_id.cache';
$robots = $cache->get($cacheKey);
if ($robots === null) {
// $robots is null because of cache expiration or data does not exist
// Make the database call and populate the variable
$robots = Robots::find(array("order" => "id"));
// Store it in the cache
$cache->save($cacheKey, $robots);
}
// Use $robots :)
foreach ($robots as $robot) {
echo $robot->name, "\n";
}
Memcached 后端存储器例子（Memcached Backend Example）¶The above example changes slightly (especially in terms of configuration) when we are using a Memcached backend. <?php
//Cache data for one hour
$frontCache = new Phalcon\Cache\Frontend\Data(array(
"lifetime" => 3600
));
// Create the component that will cache "Data" to a "Memcached" backend
// Memcached connection settings
$cache = new Phalcon\Cache\Backend\Libmemcached($frontCache, array(
"host" => "localhost",
"port" => "11211"
));
// Try to get cached records
$cacheKey = 'robots_order_id.cache';
$robots = $cache->get($cacheKey);
if ($robots === null) {
// $robots is null because of cache expiration or data does not exist
// Make the database call and populate the variable
$robots = Robots::find(array("order" => "id"));
// Store it in the cache
$cache->save($cacheKey, $robots);
}
// Use $robots :)
foreach ($robots as $robot) {
echo $robot->name, "\n";
}
查询缓存（Querying the cache）¶The elements added to the cache are uniquely identified by a key. In the case of the File backend, the key is the actual filename. To retrieve data from the cache, we just have to call it using the unique key. If the key does not exist, the get method will return null. <?php
// Retrieve products by key "myProducts"
$products = $cache->get("myProducts");
If you want to know which keys are stored in the cache you could call the queryKeys method: <?php
// Query all keys used in the cache
$keys = $cache->queryKeys();
foreach ($keys as $key) {
$data = $cache->get($key);
echo "Key=", $key, " Data=", $data;
}
//Query keys in the cache that begins with "my-prefix"
$keys = $cache->queryKeys("my-prefix");
删除缓存数据（Deleting data from the cache）¶There are times where you will need to forcibly invalidate a cache entry (due to an update in the cached data). The only requirement is to know the key that the data have been stored with. <?php
// Delete an item with a specific key
$cache->delete("someKey");
// Delete all items from the cache
$keys = $cache->queryKeys();
foreach ($keys as $key) {
$cache->delete($key);
}
检查缓存是否存在（Checking cache existence）¶It is possible to check if a cache already exists with a given key: <?php
if ($cache->exists("someKey")) {
echo $cache->get("someKey");
} else {
echo "Cache does not exists!";
}
有效期（Lifetime）¶A “lifetime” is a time in seconds that a cache could live without expire. By default, all the created caches use the lifetime set in the frontend creation. You can set a specific lifetime in the creation or retrieving of the data from the cache: Setting the lifetime when retrieving: <?php
$cacheKey = 'my.cache';
//Setting the cache when getting a result
$robots = $cache->get($cacheKey, 3600);
if ($robots === null) {
$robots = "some robots";
// Store it in the cache
$cache->save($cacheKey, $robots);
}
Setting the lifetime when saving: <?php
$cacheKey = 'my.cache';
$robots = $cache->get($cacheKey);
if ($robots === null) {
$robots = "some robots";
//Setting the cache when saving data
$cache->save($cacheKey, $robots, 3600);
}
多级缓存（Multi-Level Cache）¶This feature of the cache component, allows the developer to implement a multi-level cache. This new feature is very useful because you can save the same data in several cache locations with different lifetimes, reading first from the one with the faster adapter and ending with the slowest one until the data expires: <?php
use Phalcon\Cache\Frontend\Data as DataFrontend,
Phalcon\Cache\Multiple,
Phalcon\Cache\Backend\Apc as ApcCache,
Phalcon\Cache\Backend\Memcache as MemcacheCache,
Phalcon\Cache\Backend\File as FileCache;
$ultraFastFrontend = new DataFrontend(array(
"lifetime" => 3600
));
$fastFrontend = new DataFrontend(array(
"lifetime" => 86400
));
$slowFrontend = new DataFrontend(array(
"lifetime" => 604800
));
//Backends are registered from the fastest to the slower
$cache = new Multiple(array(
new ApcCache($ultraFastFrontend, array(
"prefix" => 'cache',
)),
new MemcacheCache($fastFrontend, array(
"prefix" => 'cache',
"host" => "localhost",
"port" => "11211"
)),
new FileCache($slowFrontend, array(
"prefix" => 'cache',
"cacheDir" => "../app/cache/"
))
));
//Save, saves in every backend
$cache->save('my-key', $data);
前端适配器（Frontend Adapters）¶The available frontend adapters that are used as interfaces or input sources to the cache are:
自定义前端适配器（Implementing your own Frontend adapters）¶The Phalcon\Cache\FrontendInterface interface must be implemented in order to create your own frontend adapters or extend the existing ones. 后端适配器（Backend Adapters）¶The backend adapters available to store cache data are:
自定义后端适配器（Implementing your own Backend adapters）¶The Phalcon\Cache\BackendInterface interface must be implemented in order to create your own backend adapters or extend the existing ones. 文件后端存储器选项（File Backend Options）¶This backend will store cached content into files in the local server. The available options for this backend are:
Memcached 后端存储器选项（Memcached Backend Options）¶This backend will store cached content on a memcached server. The available options for this backend are: APC 后端存储器选项（APC Backend Options）¶This backend will store cached content on Alternative PHP Cache (APC). The available options for this backend are:
Mongo 后端存储器选项（Mongo Backend Options）¶This backend will store cached content on a MongoDB server. The available options for this backend are:
XCache 后端存储器选项（XCache Backend Options）¶This backend will store cached content on XCache (XCache). The available options for this backend are:
There are more adapters available for this components in the Phalcon Incubator |