title: good way to Symfony 2 custom form validation, two choice fields
body: <p>In Symfony2, I have adding and editing forms with two choice fields as dropdown. The first one is containing the years and the second one is containing
  the weeks. so I would like to check that the selected year and week is not past time. I mean Its good to select and wanted to persist if year: 2013. and week: 5, 
  but its not good if the year: 2012. and week 5. and here wanna have a warning to it.</p>
  
  <p>basically I use doctrine entity manager and isValid() for validating the form right now, then I persist the object to database.</p>
  
  <p>Im a little disturbed about the many ways I have found on the net. </p>
  
  <p>so I would like to know which way is the best for me to validate these? I mean entity validate, non-entity, and where to search for it's place. :)</p>
  
  <p>thank you so much.</p>