code snippet for custom validation constraint for two fields

Person.php

class Person extends Constraint
{
    /**
     * (non-PHPdoc)
     * @see Symfony\Component\Validator.Constraint::validatedBy()
     */
    public function validatedBy()
    {
        return 'person_validator';
    }

    /**
     * (non-PHPdoc)
     * @see Symfony\Component\Validator.Constraint::getTargets()
     */
    public function getTargets()
    {
        return Constraint::CLASS_CONSTRAINT;
    }
}

PersonEntity.php

class Person
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @ORM\Column(type="string", length="255", name="firstname")
     */
    protected $firsname;

    /**
     * @ORM\Column(type="string", length="255", name="lastname")
     */
    protected $lastname;
 
    // ...

PersonType.php

    public function buildForm(FormBuilder $builder, array $options)
    {
        $builder
            ->add('firsname', 'text', array())
            ->add('lastname', 'text', array())
            ->add('username', 'text', array('property_path' => false))
            ;
    }

    /**
     * (non-PHPdoc)
     * @see Symfony\Component\Form.AbstractType::getDefaultOptions()
     */
    public function getDefaultOptions(array $options)
    {
        return array(
            'data_class' => 'Ahsio\StackBundle\Entity\Person',
            'validation_constraint' => new Person(),
        );
    }

PersonValidator.php

class PersonValidator extends ConstraintValidator
{
    protected $request;

    public function __construct(Request $request)
    {
        $this->request = $request;
    }
    /**
     * (non-PHPdoc)
     * @see Symfony\Component\Validator\ConstraintValidatorInterface::isValid()
     */
    public function isValid($value, Constraint $constraint)
    {
        var_dump($this->request->request->get('person'));die();
        return true;
    }
}

services.xml

    <services>
        <service id="person.validator" class="Ahsio\StackBundle\Validator\Constraints\PersonValidator" scope="request">
            <argument type="service" id="request" />
            <tag name="validator.constraint_validator" alias="person_validator" />
        </service>
        <!-- ... -->
    </services>