title: visualforce page render a button
body: <p>here is my code for a output field. when the field is empty the button is rendered, when the field has value the clear button will show up and allow me to empty the field and render the button again. but I can't manage it to render the button again once the field is is cleared, can anybody suggest a fix?</p>
  
  <pre><code>&lt;apex:pageBlockSectionItem &gt;
    &lt;apex:outputLabel value="Order:" for="callerorder"/&gt;
    &lt;apex:outputPanel id="callerorder"&gt;
      &lt;apex:outputField value="{!newPhoneCallRecord.Order__c}" /&gt;
      &lt;apex:commandButton value="x" rendered="{!!ISBLANK(newPhoneCallRecord.Order__c)}" rerender="phoneRecordSection"&gt;
        &lt;apex:param name="orderRMV" value="" assignTo="{!newPhoneCallRecord.Order__c}"/&gt; 
      &lt;/apex:commandButton&gt;
    &lt;/apex:outputPanel&gt;
  </code></pre>