ExpressionDependency.php 2.12 KB
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<?php
/**
 * @link http://www.yiiframework.com/
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 * @copyright Copyright (c) 2008 Yii Software LLC
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 * @license http://www.yiiframework.com/license/
 */

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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.
 * 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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 * 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).
 *
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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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	 * @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 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).
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	 */
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	public $expression;
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	/**
	 * @var mixed custom data associated with this dependency. In [[expression]], you may compare the value of
	 * this property with the latest data to determine if the dependency has changed or not.
	 */
	public $data;
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	/**
	 * Constructor.
	 * @param string $expression the PHP expression whose result is used to determine the dependency.
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	 * @param mixed $data the custom data associated with this dependency
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	 * @param array $config name-value pairs that will be used to initialize the object properties
	 */
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	public function __construct($expression = 'true', $data = null, $config = array())
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	{
		$this->expression = $expression;
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		$this->data = $data;
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		parent::__construct($config);
	}
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	/**
	 * Generates the data needed to determine if dependency has been changed.
	 * This method returns the result of the PHP expression.
	 * @return mixed the data needed to determine if dependency has been changed.
	 */
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	protected function generateDependencyData()
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	{
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		return eval("return {$this->expression};");
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	}
}