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vendor/yiisoft/yii2/caching/ExpressionDependency.php

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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).
+ *
+ * For more details and usage information on Cache, see the [guide article on caching](guide:caching-overview).
+ *
+ * @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 $expression = 'true';
+    /**
+     * @var mixed custom parameters associated with this dependency. You may get the value
+     * of this property in [[expression]] using `$this->params`.
+     */
+    public $params;
+
+
+    /**
+     * Generates the data needed to determine if dependency has been changed.
+     * This method returns the result of the PHP expression.
+     * @param CacheInterface $cache the cache component that is currently evaluating this dependency
+     * @return mixed the data needed to determine if dependency has been changed.
+     */
+    protected function generateDependencyData($cache)
+    {
+        return eval("return {$this->expression};");
+    }
+}