yii2

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<?php
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/**
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 * @link https://www.yiiframework.com/
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 * @copyright Copyright (c) 2008 Yii Software LLC
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 * @license https://www.yiiframework.com/license/
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 */
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namespace yii\caching;
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/**
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 * ExpressionDependency represents a dependency based on the result of a PHP expression.
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 *
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 * ExpressionDependency will use `eval()` to evaluate the PHP expression.
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 * The dependency is reported as unchanged if and only if the result of the expression is
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 * the same as the one evaluated when storing the data to cache.
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 *
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 * A PHP expression can be any PHP code that has a value. To learn more about what an expression is,
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 * please refer to the [php manual](https://www.php.net/manual/en/language.expressions.php).
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 *
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 * For more details and usage information on Cache, see the [guide article on caching](guide:caching-overview).
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 *
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 * @author Qiang Xue <qiang.xue@gmail.com>
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 * @since 2.0
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 */
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class ExpressionDependency extends Dependency
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{
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    /**
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     * @var string the string representation of a PHP expression whose result is used to determine the dependency.
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     * A PHP expression can be any PHP code that evaluates to a value. To learn more about what an expression is,
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     * please refer to the [php manual](https://www.php.net/manual/en/language.expressions.php).
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     */
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    public $expression = 'true';
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    /**
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     * @var mixed custom parameters associated with this dependency. You may get the value
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     * of this property in [[expression]] using `$this->params`.
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     */
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    public $params;
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    /**
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     * Generates the data needed to determine if dependency has been changed.
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     * This method returns the result of the PHP expression.
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     * @param CacheInterface $cache the cache component that is currently evaluating this dependency
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     * @return mixed the data needed to determine if dependency has been changed.
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     */
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    protected function generateDependencyData($cache)
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    {
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        return eval("return {$this->expression};");
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    }
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}
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