function searchpidx() {
  var sSearch = $F("uindex");

  if (sSearch.length < 6) { return false; }

new Ajax.Request('post.php',
  {
    method:'get',
    parameters: { search: sSearch },
    onSuccess: function(transport){
      var response = transport.responseText;
      document.getElementById('city').value = response;
    }
  });

}