A modern translateable behavior for the Yii framework.
The preferred way to install this extension is through composer.
Either run
$ composer require creocoder/yii2-translateableor add
"creocoder/yii2-translateable": "~1.0"
to the require section of your composer.json file.
Run the following command
$ yii migrate/create create_post_tableOpen the /path/to/migrations/m_xxxxxx_xxxxxx_create_post_table.php file,
inside the up() method add the following
$this->createTable('{{%post}}', [
    'id' => Schema::TYPE_PK,
]);Run the following command
$ yii migrate/create create_post_translation_tableOpen the /path/to/migrations/m_xxxxxx_xxxxxx_create_post_translation_table.php file,
inside the up() method add the following
$this->createTable('{{%post_translation}}', [
    'post_id' => Schema::TYPE_INTEGER . ' NOT NULL',
    'language' => Schema::TYPE_STRING . '(16) NOT NULL',
    'title' => Schema::TYPE_STRING . ' NOT NULL',
    'body' => Schema::TYPE_TEXT . ' NOT NULL',
]);
$this->addPrimaryKey('', '{{%post_translation}}', ['post_id', 'language']);Configure model as follows
use creocoder\translateable\TranslateableBehavior;
/**
 * ...
 * @property string $title
 * @property string $body
 * ...
 */
class Post extends \yii\db\ActiveRecord
{
    public function behaviors()
    {
        return [
            'translateable' => [
                'class' => TranslateableBehavior::className(),
                'translationAttributes' => ['title', 'body'],
                // translationRelation => 'translations',
                // translationLanguageAttribute => 'language',
            ],
        ];
    }
    public function transactions()
    {
        return [
            self::SCENARIO_DEFAULT => self::OP_INSERT | self::OP_UPDATE,
        ];
    }
    public function getTranslations()
    {
        return $this->hasMany(PostTranslation::className(), ['post_id' => 'id']);
    }
}Model PostTranslation can be generated using Gii.
To set translations to the entity
$post = new Post();
// title attribute translation for default application language
$post->title = 'Post title';
// body attribute translation for default application language
$post->body = 'Post body';
// title attribute translation for German
$post->translate('de-DE')->title = 'Post titel';
// body attribute translation for German
$post->translate('de-DE')->body = 'Post inhalt';
// title attribute translation for Russian
$post->translate('ru-RU')->title = 'Заголовок поста';
// body attribute translation for Russian
$post->translate('ru-RU')->body = 'Тело поста';
// save post and its translations
$post->save();To get translations from the entity
$posts = Post::find()->with('translations')->all();
foreach ($posts as $post) {
    // title attribute translation for default application language
    $title = $post->title;
    // body attribute translation for default application language
    $body = $post->body;
    // title attribute translation for German
    $germanTitle = $post->translate('de-DE')->title;
    // body attribute translation for German
    $germanBody = $post->translate('de-DE')->body;
    // title attribute translation for Russian
    $russianTitle = $post->translate('ru-RU')->title;
    // body attribute translation for Russian
    $russianBody = $post->translate('ru-RU')->body;
}To check translations in the entity
$post = Post::findOne(1);
// checking for default application language translation
$result = $post->hasTranslation();
// checking for German translation
$result = $post->hasTranslation('de-DE');
// checking for Russian translation
$result = $post->hasTranslation('ru-RU');Example of controller actions
class PostController extends Controller
{
    public function actionCreate()
    {
        $model = new Post();
        foreach (Yii::$app->request->post('PostTranslation', []) as $language => $data) {
            foreach ($data as $attribute => $translation) {
                $model->translate($language)->$attribute = $translation;
            }
        }
        //...
    }
    public function actionUpdate($id)
    {
        $model = Post::find()->with('translations')->where(['id' => $id])->one();
        if ($model === null) {
            throw new NotFoundHttpException('The requested page does not exist.');
        }
        foreach (Yii::$app->request->post('PostTranslation', []) as $language => $data) {
            foreach ($data as $attribute => $translation) {
                $model->translate($language)->$attribute = $translation;
            }
        }
        //...
    }
}Example of view form
<?php
use yii\helpers\Html;
use yii\widgets\ActiveForm;
$form = ActiveForm::begin();
foreach (['en-US', 'de-DE', 'ru-RU'] as $language) {
    echo $form->field($model->translate($language), "[$language]title")->textInput();
    echo $form->field($model->translate($language), "[$language]body")->textarea();
}
//...
ActiveForm::end();Example of model attribute labels
class PostTranslation extends \yii\db\ActiveRecord
{
    public function attributeLabels()
    {
        switch ($this->language) {
            case 'de-DE':
                return [
                    'title' => 'Titel',
                    'body' => 'Inhalt',
                ];
            case 'ru-RU':
                return [
                    'title' => 'Заголовок',
                    'body' => 'Тело',
                ];
            default:
                return [
                    'title' => 'Title',
                    'body' => 'Body',
                ];
        }
    }
}Support this project and others by creocoder via gratipay.