'language' => 'en-US',

'sourceLanguage' => 'zh-CN',

'i18n' => [

            'translations' => [

                '*' => [

                    'class' => 'yii\i18n\PhpMessageSource',

                    //'basePath' => '/messages',

                    'fileMap' => [

                        'collection' => 'collection.php'

                    ],

                ],

            ],

        ],

Yii::t('app', 'This is a string to translate!');