function encode_form(id){
  var form = document.getElementById(id);
  if(form === null) return null;
  var inputs = form.children;
  var out_encoded_data = "";
  for(var i=0; i < inputs.length; i++){
    if(inputs[i].tagName == "INPUT" || inputs[i].tagName == "TEXTAREA" || inputs[i].tagName == "SELECT"){
      if(out_encoded_data == ""){
        out_encoded_data += inputs[i].name + "=" + encodeURIComponent(inputs[i].value);
      }else{
        out_encoded_data += "&" + inputs[i].name + "=" + encodeURIComponent(inputs[i].value);
      }
    }
  }
  return out_encoded_data;
}