Yii2 translation does not work

You Just Follow This Steps……

Step 1: In the common directory , create messages folder.

Step 2: Create i18n.php file inside common/config directory with following content:

<?php
return [
    'sourcePath' => __DIR__. '..' . DIRECTORY_SEPARATOR . '..' . DIRECTORY_SEPARATOR . '..' .    DIRECTORY_SEPARATOR,
    'languages' => ['en-EN', 'ru-RU'], //Add languages to the array for the language files to be generated, here are English and Russian.
    'translator' => 'Yii::t',
    'sort' => false,
    'removeUnused' => false,
    'only' => ['*.php'],
    'except' => [
        '.svn',
        '.git',
        '.gitignore',
        '.gitkeep',
        '.hgignore',
        '.hgkeep',
        '/messages',
        '/vendor',
    ],
    'format' => 'php',
    'messagePath' => __DIR__ . DIRECTORY_SEPARATOR . '..' . DIRECTORY_SEPARATOR .      'messages', //path of messages folder created above
    'overwrite' => true,
];

Note: Make sure to add all required languages to ‘languages’ array. In the above example I have added English and Russian for Generate Yii2 Framework multi language.

Step 3: Add the i18n component in config file common/main.php configuration as follows:

'components' => [
    ...
    'i18n' => [
        'translations' => [
            'frontend*' => [
                'class' => 'yii\i18n\PhpMessageSource',
                'basePath' => '@common/messages',
            ],
            'backend*' => [
                'class' => 'yii\i18n\PhpMessageSource',
                'basePath' => '@common/messages',
            ],
        ],
    ],
    ...
],

Step 4:

Add the language module in common config file to use the default language on your app, such as:

'language' => 'en-EN' inside common/main.php.

You now can use Yii::$app->language = ‘en-EN’ at any runtime like URL request, query code.

Note: In any Model, Controller Generate by Gii, you can see Enable I18n ticket choice, just enable this for Multi language. Gii Tool will auto generate a Model has pre-defined as below, due to frontent or backend folder:

Yii::t('frontend', 'Translatable String');

Yii::t('backend', 'Translatable String');

Step 5: Run this command line from Yii2 app folder:

yii message/extract @common/config/i18n.php

This command line will Generate Yii2 Framework multi language translation files inside common/messages and divide into frontend and backend folder.

For example: Yii message will generate the translation files as follows:
common/
 .....
       messages/
            en-EN/
                  backend.php
                  frontend.php
            ru-RU/
                  backend.php
                  frontend.php
 .....

If you want to edit the translate text, just open backend.php or frontend.php file and edit.