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Page Caching
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============
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Page caching refers to caching the content of a whole page on the server side. Later when the same page
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is requested again, its content will be served from the cache instead of regenerating it from scratch.
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Page caching is supported by [[yii\filters\PageCache]], an [action filter](structure-filters.md).
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It can be used like the following in a controller class:
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```php
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public function behaviors()
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{
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return [
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[
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'class' => 'yii\filters\PageCache',
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'only' => ['index'],
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'duration' => 60,
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'variations' => [
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\Yii::$app->language,
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],
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'dependency' => [
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'class' => 'yii\caching\DbDependency',
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'sql' => 'SELECT COUNT(*) FROM post',
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],
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],
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];
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}
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```
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The above code states that page caching should be used only for the `index` action; the page content should
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be cached for at most 60 seconds and should be variated by the current application language;
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and the cached page should be invalidated if the total number of posts is changed.
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As you can see, page caching is very similar to [fragment caching](caching-fragment.md). They both support options such
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as `duration`, `dependencies`, `variations`, and `enabled`. Their main difference is that page caching is
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implemented as an [action filter](structure-filters.md) while fragment caching a [widget](structure-widgets.md).
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You can use [fragment caching](caching-fragment.md) as well as [dynamic content](caching-fragment.md#dynamic-content)
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together with page caching.
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