symfony2 Expression validation
use Symfony\Component\Validator\Constraints as Assert;
class Conference
{
/**
* @var \DateTime
*
* @Assert\Expression(
* "this.startDate <= this.endDate",
* message="Start date should be less or equal to end date!"
* )
*/
protected $startDate;
/**
* @var \DateTime
*
* @Assert\Expression(
* "this.endDate >= this.startDate",
* message="End date should be greater or equal to start date!"
* )
*/
protected $endDate;
}