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