title: Doctrine enum type not allows non enumerated values to be added?
body: <p>I'm brand new to Doctrine and Code Igniter and I'm running into a problem with one of my tables.</p>
  
  <p>I have a model that I thought would only allow 4 different letters (for testing at this point in time)</p>
  
  <pre><code>&lt;?php
  class Photo extends Doctrine_Record 
  {
      public function setTableDefinition() 
      {
          $this-&gt;hasColumn('photo_path', 'string', 255, array('unique' =&gt; 'true'));       
          $this-&gt;hasColumn('category', 'enum', null,
              array('values' =&gt; array('a', 'b', 'c', 'd'))
          );
          $this-&gt;hasColumn('token', 'string', 255);
      }
  
      public function setUp() 
      {       
          $this-&gt;actAs('Timestampable');      
      }
  
      public function preInsert($event) 
      {
          $this-&gt;token = (sha1(rand(11111, 99999)));  
      }
  }
  </code></pre>
  
  <p>I have a view that has a select box and an upload form</p>
  
  <pre><code>&lt;?php echo validation_errors('&lt;p class="error"&gt;','&lt;/p&gt;'); ?&gt;
      &lt;div id="upload"&gt;
          &lt;?php
          $categoryOptions= array(
          '' =&gt; '',
          'a' =&gt; 'a',
          'b' =&gt; 'b',
          'c' =&gt; 'c',
          '1' =&gt; '1'
          );
          echo form_open_multipart('admin/addImage');
          echo form_upload('userfile');
          echo form_dropdown('letter', $categoryOptions);
          echo form_submit('upload', 'Upload!');
          echo form_close();      
          ?&gt;
      &lt;/div&gt;
  </code></pre>
  
  <p>When I select '1' from the select box, I would expect Doctrine to throw an error and not insert that record, however it will insert it with a category of '1'. Is there some step I'm not doing so that the enum column restricts the input?</p>
  
  <p>Thanks in advance.</p>