title: Validation for "at least one phone number is required" in CakePHP
body: <p>This is the model file <code>vechile_enquiry.php</code></p>
  
  <pre><code>&lt;?php
      class VechileEnquiry  extends AppModel{
          var $name ='VechileEnquiry';
          var $validate = array('name' =&gt; array
                                              ('rule' =&gt; 'notEmpty',
                                              'message' =&gt; 'Please type name')
                              );
      }
  ?&gt;
  </code></pre>
  
  <p>This is the view file <code>vechile.ctp</code></p>
  
  <pre><code>&lt;?php
      echo $this-&gt;Form-&gt;input('name', array('label'=&gt;false));
  ?&gt;
  </code></pre>
  
  <p>At least one phone number is required:</p>
  
  <pre><code>&lt;?php
      echo $this-&gt;Form-&gt;input('mobile_phone', array('label'=&gt;false));
      echo $this-&gt;Form-&gt;input('work_phone', array('label'=&gt;false));
      echo $this-&gt;Form-&gt;input('home_phone', array('label'=&gt;false));
  ?&gt;
  </code></pre>
  
  <p>Validation is working in the name field but I'm not getting how to implement validation in <code>mobile_phone</code>,
  <code>work_phone</code>, <code>home_phone</code> for the condition that at least one phone number is required.</p>