Yii offers a shorthand of sorts to refer to file paths and URLs so that you do not have to hard-code these into your application. They are basically defined constants and always are prefixed with an @ symbol.
8.1 Commonly Used Predefined Aliases
There are a number of predefined aliases available to you by default. Some of the more commonly used aliases are as follows:
- @yii: The path to the core Yii application files.
- @app: A reference to the root path of the application.
- @web: The base URL pointing to your application.
- @webroot: The document root directory as specified in your Apache config.
Yii2 Advanced Template defines these additional aliases:
- @common: Path to the 'common' root directory.
- @frontend: Path to the 'frontend' root directory.
- @backend: Path to the 'backend' root directory.
- @console: Path to the 'console' root directory.
8.2 Defining Aliases
You can define your own aliases by using the setAlias function.
To set an alias of a file path, you would use the following format:
You can also set an alias to a URL as such:
You can even use an alias to define another alias:
You also have the option to set any aliases in the config file. You could add the following to the $config array:
'aliases' => [
'@foo' => '/path/to/foo',
'@bar' => 'http://www.example.com',
8.3 Resolving Aliases
You get the alias value by using Yii::getAlias(). If @foo and @bar where set as above, you would access them as such:
$foo = Yii::getAlias('@foo');
$bar = Yii::getAlias('@foo');
If you echoed these out, you would get the following:
You can also append additional path directors.
8.4 Using Aliases
Aliases are recognized in many places in Yii without needing to call Yii::getAlias() to convert them into paths or URLs. Sometimes the @alias is used as part of the path.
For example, setting the path to the file cache, you would do as such:
$cache = new FileCache([
'cachePath' => '@runtime/cache',