AdvertTranslation.php

class Translation {
 
   public static function fromDTO($dto) {
       $translation = new static($dto->locale);
       $translation->address = $dto->address;
       // ...
       
       return $translation;
   }
 
   public static function  createTranslationSetFromDTO($dto) {
      if (!is_array($dto)) return []; 
      
      return array_map(function ($translationDTO) {
          return static::fromDTO($translationDTO); 
      }, $dto);
   }
}

dto.php

<?php

class DTO {
   private $data;
   
   public function __construct($data) {
        $this->data = $data;
   }
   
   public function __isset($name) {
       return isset($this->data->$name));
   }
   
   public function __get($name) {
        if (!isset($this->data->$name)) return null;
        
        if (is_object($this->data->$name)) {
            return new static($this->data->$name);
        }
        
        if (!is_array($this->data->$name) {
            return $this->data->$name;
        }
        
        $result = [];
        foreach($this->data->$name as $item) {
            if (is_object($this->data->$name)) {
                $result[] = new static($this->data->$name);
            }       
        }
        
        return $result;
   }
}

test.php

 <?php

$advert
 ->setBathroom($dto->bathroom)
 ->setBedroom($dto->bedroom)
 ->setZipCode($dto->zipCode)
 ->setPrice(Money::fromDTO($dto->price))
 ->setPoint(Point::fromDTO($dto->location))
 // создает ArrayCollection и заменяет
 ->translate(Translation::createTranslationSetFromDTO($dto->translations));
  
$errors = $this->validator->validate($advert);