trait CustomerTrait {
	/**
     * @ORM\Column(name="customer_type", type="string", length=255, nullable=true)
     * @Eccube\FormAppend(
     *  auto_render=true,
     *  type="\Symfony\Component\Form\Extension\Core\Type\ChoiceType",
     *  options={
     *    "required": true,
     *    "label": "会員種類",
     *    "choices": {"一般会員": "normal","プレミアム会員": "premium",},
     *  }
     * )
     */
    private $customer_type;
    
    public function getcustomertype() {
        return $this->customer_type;
    }
    
    public function setcustomertype($customer_type) {
        $this->customer_type = $customer_type;

        return $this;
    }
    
    //(…中略)
}

->add('customer_type', ChoiceType::class, [
                'required' => true,
                'expanded' => false,
                'multiple' => false,
                'label' => '会員種類',
                'choices'  => [
                    '一般会員'   => 'normal',
                    'プレミアム会員' => 'premium',
                ],
                'eccube_form_options' =>
                [
                    'auto_render' => true,
                    'form_theme' => null,
                    'style_class' => 'ec-select',
                ]
            ]);