Path aliases

In Yii2, path aliases are used to represent file paths or URL paths so that we don't hardcode paths or URLs directly into our application. In Yii2, aliases always start with the @ symbol so that Yii knows how to differentiate it from a file path or URL.

Aliases can be defined in several ways. The most basic way to define a new alias is to call \Yii::setAlias():

\Yii::setAlias('@path', '/path/to/example');
\Yii::setAlias('@example, 'https://www.example.com');

Aliases can also be defined in the application configuration file by setting the alias option as follows:

return [
    // ...
    'aliases' => [
        '@path => '/path/to/example,
        '@example' => 'https://www.example.com',
    ],
];

Also, aliases can be easily retrieved using \Yii::getAlias():

\Yii::getAlias('@path') // returns /path/to/example
\Yii::getAlias('@example') // returns https://www.example.com

Several places in Yii are alias-aware and will accept aliases as inputs. For example, yii\caching\FileCache accepts a file alias as an alias for the $cachePath parameter:

$cache = new FileCache([
    'cachePath' => '@runtime/cache',
]);

Note

For more information on path aliases, check out the Yii documentation at http://www.yiiframework.com/doc-2.0/guide-concept-aliases.html.