title: How to handle exceptions on Doctrine 2 validation
body: <p>I'm new to Doctrine 2 (and exceptions in PHP, really), but am trying to come up with a robust validation engine on Doctrine 2 (on top of CodeIgniter), following <a href="http://www.doctrine-project.org/blog/doctrine2-validations" rel="nofollow noreferrer">this page</a>.</p>
  
  <p>Right now I'm wondering where I would define the ValidateException class, and how to 'try' doing a save (persist?) on my entity (from a controller, library, etc).</p>
  
  <p>I'd like to have something where, after doing this (in an 'authentication' library, for example):</p>
  
  <pre><code>$user-&gt;username = $username;
  $user-&gt;email_address = $email_address;
  $user-&gt;password = $password;
  
  $em-&gt;persist($user);
  $em-&gt;flush();
  
  return $foo; //where $foo refers to whether $em-&gt;flush() worked...
  </code></pre>
  
  <p>I could simply return whether that persistence was successful (i.e., passed validation and saved), or not successful (i.e., failed validation).</p>