如果其他字段具有特定值，则Symfony验证字段

use Symfony\Component\Form\FormEvent;
use Symfony\Component\Form\FormEvents;
use Symfony\Component\Validator\Constraints\NotBlank;
use Symfony\Component\Validator\Constraints\Length;
use Symfony\Component\Validator\Validation;

// 创建表单构建器
$builder = $this->createFormBuilder();

// 添加需要验证的字段
$builder->add('field1');
$builder->add('field2');

// 添加事件监听器
$builder->addEventListener(FormEvents::PRE_SUBMIT, function (FormEvent $event) {
    $form = $event->getForm();
    $data = $event->getData();

    // 根据其他字段的值进行验证
    if ($data['field1'] === 'specific_value') {
        $form->add('field3', null, [
            'constraints' => [
                new NotBlank(),
                new Length(['min' => 5]),
            ],
        ]);
    }
});

// 构建表单
$form = $builder->getForm();