ExpressionDependency

API reference › yii › caching › ExpressionDependency

class	`yii\caching\ExpressionDependency`
Extends	`Dependency` » `yii\base\BaseObject`
Implements	`yii\base\Configurable`
Since	2.0
Source	`framework/caching/ExpressionDependency.php`

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.

For more details and usage information on Cache, see the guide article on caching.

Properties

Property	Type	Description	Defined by
`$data`	`mixed`	The dependency data that is saved in cache and later is compared with the latest dependency data. Default: `null`.	`Dependency`
`$expression`	`string`	The string representation of a PHP expression whose result is used to determine the dependency. Default: `'true'`.	`ExpressionDependency`
`$params`	`mixed`	Custom parameters associated with this dependency. Default: `null`.	`ExpressionDependency`
`$reusable`	`bool`	Whether this dependency is reusable or not. Default: `false`.	`Dependency`

Methods

Method	Description	Defined by
`__construct()`	Constructor.	`yii\base\BaseObject`
`__call()`	Calls the named method which is not a class method.	`yii\base\BaseObject`
`__get()`	Returns the value of an object property.	`yii\base\BaseObject`
`__isset()`	Checks if a property is set, i.e. defined and not null.	`yii\base\BaseObject`
`__set()`	Sets value of an object property.	`yii\base\BaseObject`
`__unset()`	Sets an object property to null.	`yii\base\BaseObject`
`canGetProperty()`	Returns a value indicating whether a property can be read.	`yii\base\BaseObject`
`canSetProperty()`	Returns a value indicating whether a property can be set.	`yii\base\BaseObject`
`className()` static	Returns the fully qualified name of this class.	`yii\base\BaseObject`
`evaluateDependency()`	Evaluates the dependency by generating and saving the data related with dependency.	`Dependency`
`hasMethod()`	Returns a value indicating whether a method is defined.	`yii\base\BaseObject`
`hasProperty()`	Returns a value indicating whether a property is defined.	`yii\base\BaseObject`
`init()`	Initializes the object.	`yii\base\BaseObject`
`isChanged()`	Checks whether the dependency is changed.	`Dependency`
`resetReusableData()` static	Resets all cached data for reusable dependencies.	`Dependency`
`generateDependencyData()` protected	Generates the data needed to determine if dependency has been changed.	`ExpressionDependency`
`generateReusableHash()` protected	Generates a unique hash that can be used for retrieving reusable dependency data.	`Dependency`

Property details

$expression

public string $expression = 'true'

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.

$params

public mixed $params = null

Custom parameters associated with this dependency.

You may get the value of this property in $expression using $this->params.

Method details

generateDependencyData()

protected function generateDependencyData(yii\caching\CacheInterface $cache): mixed

Generates the data needed to determine if dependency has been changed.

This method returns the result of the PHP expression.

Parameters

Parameter	Type	Description
`$cache`	`CacheInterface`	The cache component that is currently evaluating this dependency

Returns

mixed: The data needed to determine if dependency has been changed.