Internationalization configuration and changing languages


1.I don’t understand when in guide they say yii\base\Application: language should be configured and they give an example of “ru-RU”. My question is what if I have 3 languages in which I have to translate (how can I configure that). SourceLanguage is English and languages to translate to are: Spanish, French and Portigues.

2.I would like the user to change the language of the application dynamically using a combobox or link but I wonder about how to send the parameter to server so that the server knows that the user required to change the language(for instance en to Spanish)

Here is also one good tutorial: