silverstripe-framework/docs/en/reference/flushable.md

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# Flushable
## Introduction
Allows a class to define it's own flush functionality, which is triggered when `flush=1` is requested in the URL.
`[api:FlushRequestFilter]` is run before a request is made, calling `flush()` statically on all
implementors of `[api:Flushable]`.
## Usage
To use this API, you need to make your class implement `[api:Flushable]`, and define a `flush()` static function,
this defines the actions that need to be executed on a flush request.
### Using with SS_Cache
This example uses `[api:SS_Cache]` in some custom code, and the same cache is cleaned on flush:
:::php
<?php
class MyClass extends DataObject implements Flushable {
public static function flush() {
SS_Cache::factory('mycache')->clean(Zend_Cache::CLEANING_MODE_ALL);
}
public function MyCachedContent() {
$cache = SS_Cache::factory('mycache')
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$something = $cache->load('mykey');
if(!$something) {
$something = 'value to be cached';
$cache->save($something);
}
return $something;
}
}
### Using with filesystem
Another example, some temporary files are created in a directory in assets, and are deleted on flush. This would be
useful in an example like `GD` or `Imagick` generating resampled images, but we want to delete any cached images on
flush so they are re-created on demand.
:::php
<?php
class MyClass extends DataObject implements Flushable {
public static function flush() {
foreach(glob(ASSETS_PATH . '/_tempfiles/*.jpg') as $file) {
unlink($file);
}
}
}