common/config/main.php

<?php
return [
    'vendorPath' => dirname(dirname(__DIR__)) . '/vendor',
    'components' => [
        'cache' => [
            'class' => 'yii\caching\FileCache',
        ],
        'urlManager' => [
            'enablePrettyUrl' => true,
            'showScriptName' => false,
            'class'=> 'common\components\LangUrlManager',
            'rules'=>[
                '/' => 'site/index',
                '<controller:\w+>/<action:\w+>/*'=>'<controller>/<action>',
            ]
        ],
        'request' => [
            'class' => 'common\components\LangRequest'
        ],
        'i18n' => [
            'translations' => [
                '*' => [
                    'class' => 'yii\i18n\PhpMessageSource',
                    'basePath' => $_SERVER['DOCUMENT_ROOT'].'/common/translation', 
                    'fileMap' => [
                        'app' => 'app.php',
                        'app/error' => 'error.php', 
                    ],
                ],
            ],
        ],
    ],
];