Максим Тимофеев

$customers = Customer::find()
    ->select([
        '{{customer}}.*', // получить все атрибуты покупателя
        'COUNT({{order}}.id) AS ordersCount' // вычислить количество заказов
    ])
    ->joinWith('orders') // обеспечить построение промежуточной таблицы
    ->groupBy('{{customer}}.id') // сгруппировать результаты, чтобы заставить агрегацию работать
    ->all();

cd domains\basic
php init

1. yii\caching\ApcCache: uses PHP APC extension. This option can be considered as the fastest one when dealing with cache for a centralized thick application (e.g. one server, no dedicated load balancers, etc.).
   
2. yii\caching\DbCache: uses a database table to store cached data. To use this cache, you must create a table as specified in yii\caching\DbCache::$cacheTable.
   
3. yii\caching\DummyCache: serves as a cache placeholder which does no real caching. The purpose of this component is to simplify the code that needs to check the availability of cache. For example, during development or if the server doesn't have actual cache support, you may configure a cache component to use this cache. When an actual cache support is enabled, you can switch to use the corresponding cache component. In both cases, you may use the same code Yii::$app->cache->get($key) to attempt retrieving data from the cache without worrying that Yii::$app->cache might be null.
   
4. yii\caching\FileCache: uses standard files to store cached data. This is particularly suitable to cache large chunk of data, such as page content.
   
5. yii\caching\MemCache: uses PHP memcache and memcached extensions. This option can be considered as the fastest one when dealing with cache in a distributed applications (e.g. with several servers, load balancers, etc.)
   
6. yii\redis\Cache: implements a cache component based on Redis key-value store (redis version 2.6.12 or higher is required).
   
7. yii\caching\WinCache: uses PHP WinCache (see also) extension.
   
8. yii\caching\XCache: uses PHP XCache extension.
   
9. Zend Data Cache as the underlying caching medium.
   

Как правильно передавать post данные

чтобы контроллер их видел и обрабатывал

$_POST //тут пост запрос, как обычно в php
Yii::$app->request->post() //тоже самое, но средствами yii

if(Yii::$app->request->isPost){
   $post = Yii::$app->request->post();
   echo $post['some_data'];
}else{
   echo 'не пришел post запрос, плачем всем отделом';
}

echo '/images/originals/'.$model->imagename;  //оригиналы
echo '/images/small/'.$model->imagename;  //миниатюры

echo '/images/2017/07/original/'.$model->imagename;  //оригиналы
echo '/images/2017/07/400x400/'.$model->imagename;  //миниатюры 400x400
echo '/images/2017/07/1000x/'.$model->imagename;  //миниатюры 1000xauto
echo '/images/2017/07/x50/'.$model->imagename;  //миниатюры autox50

public function getImages(){
   return $this->hasMany(Images::classname(),['id_production'=>'id']);
}

$dataProvider = new ActiveDataProvider([
    'query' => Production::find()
            ->with('images')
            ->where(['status' => 1])
            ->orderBy('id DESC')->limit(12) //обычно лимит задает Pager, но Вам виднее
]);

foreach($model->images as $image){
echo $image->imagepath;
}
//или например взять первый объект из массива объектов
echo $model->images[0]->imagepath;