title: beforeSave callback doesn't work in CakePHP
body: <p>In my Menu model I'm trying to fill the slug field if the user didn't fill it.</p>
  
  <pre><code>Model/Menu.php
  
      public function beforeSave($options = array()){
              if(
                  isset($this-&gt;data[$this-&gt;alias]['name']) &amp;&amp; 
                  !isset($this-&gt;data[$this-&gt;alias]['slug'])
              ){
                       //than fill the slug field in the db for the user.
                  $this-&gt;data[$this-&gt;alias]['slug'] = strtolower(Inflector::slug($this-&gt;data[$this-&gt;alias]['name'], '-'));
              }
          }//end function
  </code></pre>
  
  <p>but it doesn't work all the data are saved without going throught this method.</p>