title: How to send parameter POST method in AJAX
body: <p>On my site I have combobox in php:</p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
  function showUserVisits(reservationObjectId)
  {
      //alert(reservationObjectId);
      if (reservationObjectId == "")
      {
          document.getElementById("txtHint").innerHTML="";
          return;
      }
      if (window.XMLHttpRequest)
      {// code for IE7+, Firefox, Chrome, Opera, Safari
          xmlhttp=new XMLHttpRequest();
      }
      else
      {// code for IE6, IE5
          xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
  
      xmlhttp.onreadystatechange=function()
      {
          if (xmlhttp.readyState==4 &amp;&amp; xmlhttp.status==200)
          {
              document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
          }
      }
  
      xmlhttp.open("GET","get_user.php?q=" +reservationObjectId,true);
      xmlhttp.send();
  }       
  &lt;/script&gt;
  </code></pre>
  
  <p></p>
  
  <pre><code>&lt;form&gt;
      &lt;select name="users" onchange="showUserVisits(this.value)"&gt;
      &lt;!-- &lt;option value=""&gt;Select a person:&lt;/option&gt; --&gt;
      &lt;option value="1"&gt;aaa1&lt;/option&gt;
      &lt;option value="2"&gt;aaa2&lt;/option&gt;
      &lt;option value="3"&gt;aaa3&lt;/option&gt;
      &lt;option value="4"&gt;aaa4&lt;/option&gt;
      &lt;/select&gt;
      &lt;/form&gt;
  </code></pre>
  
  <p>When user change item in combobox, method showUserVisits is called by ajax. And I must pass reservationObjectId to get_user.php site. How it is done GET method, by I want to pass this parameter by POST method because in GET method someone can change id. How can I do it ?</p>
  
  <p>Thanks</p>