title: How to get form element value inside Zend_Form::isValid() method?
body: <p>I'm looking for best way of getting form element values inside isValid() method.</p>
  
  <p>I had something like this isValid():</p>
  
  <pre><code>public function isValid($data) {
  
      $start = (int)($data['start_hour'] . $data['start_minute']);
      $end   = (int)($data['end_hour'] . $data['end_minute']);
  
      if ($start &gt;= $end) {
          $this-&gt;getElement('start_hour')-&gt;addError('Start time should be less than end time');
          return false;
      }
  
      return parent::isValid($data);
  }
  </code></pre>
  
  <p>but problem is that when my data structure changes I have to change validation too.
  For example, now values of <strong>start_hour</strong>, <strong>start_minute</strong>, etc becomes elements of multidimensional array, and I need edit validation like</p>
  
  <pre><code>public function isValid($data) {
  
      $start = (int)($data['send']['start_hour'] . $data['send']['start_minute']);
      $end   = (int)($data['send']['end_hour'] . $data['send']['end_minute']);
  
      .......
  }
  </code></pre>
  
  <p>It would be great to get value of element by permanent key (like element name), so my isValid could looks like:</p>
  
  <pre><code>public function isValid($data) {
  
      $start = (int)($this-&gt;getElement('start_hour')-&gt;getValue() . $this-&gt;getElement('start_minute')-&gt;getValue());
      $end   = (int)($this-&gt;getElement('end_hour')-&gt;getValue() . $this-&gt;getElement('end_minute')-&gt;getValue());
  
      .......
  }
  </code></pre>
  
  <p>but <strong>$this->getElement('start_hour')->getValue()</strong> inside validation method return an empty value.</p>
  
  <p>Is this possible to get element value in such way?</p>
  
  <p>Thanks.</p>