Merge pull request #2177 from Ragazzo/i18n_default_category_docs

docs/guide/i18n.md

@@ -78,7 +78,7 @@ Yii tries to load appropriate translation from one of the message sources define
 ```
 
 In the above `app*` is a pattern that specifies which categories are handled by the message source. In this case we're
-handling everything that begins with `app`.
+handling everything that begins with `app`. You can also specify default translation, for more info see [this](specifying-default-translation) example.
 
 `class` defines which message source is used. The following message sources are available:
 
@@ -287,6 +287,32 @@ extension.
 Examples
 --------
 
+###Specifying default translation
+
+You can specify default translation that will be used as a fallback for categories that don't match any other translation.
+This translation should be marked with `*`. In order to do it add the following to the config file (for the `yii2-basic` application it will be `web.php`):
+
+```php
+//configure i18n component
+
+'i18n' => [
+	'translations' => [
+		'*' => [
+			'class' => 'yii\i18n\PhpMessageSource'
+		],
+	],
+],
+```
+
+Now you can use categories without configuring each one that is similar to Yii 1.1 behavior.
+Messages for the category will be loaded from a file under default translation `basePath` that is `@app/messages`:
+
+```php
+echo Yii::t('not_specified_category', 'message from unspecified category');
+```
+
+Message will be loaded from `@app/messages/<LanguageCode>/not_specified_category.php`.
+
 ###Translating module messages
 
 If you want to translate messages for a module and avoid using a single translation file for all messages, you can make it like the following: