private $name_en;
    public function setNameEn($name_en)
    {
        $this->name_en = $name_en;
        return $this;
    }
    public function getNameEn()
    {
        return $this->name_en;
    }

$builder
    ->add('name_en', 'text', array(
        'label' => '商品名(英名)',
    ))

Eccube\Entity\Product:
    fields:
        name_en:
            type: text
            nullable: true
            length: 65535

{{ form_row(form.name_en) }}