Ajax e DHTML

Respondendo a um comentário no artigo Tutorial prototype -> Ajax.Updater vou passar o conteúdo do arquivo cargamenu.php, que é simplesmente mostrar uma string com tag LI:

<?php
header("Content-type: text/html; charset=ISO-8859-1");
echo "<ul>";
switch ($_REQUEST["item"]){
  case "cidade":
    echo "<li>São Paulo</li>";
    echo "<li>Araraquara</li>";
    echo "<li>Araras</li>";
    echo "<li>Ribeirão Preto</li>";
    echo "<li>Campinas</li>";
    echo "<li>São Carlos</li>";
    echo "<li>Curitiba</li>";
    echo "<li>Florianópolis</li>";
    break;
  case "estado":
    echo "<li>Rio de Janeiro</li>";
    echo "<li>Paraná</li>";
    echo "<li>Mato Grosso</li>";
    echo "<li>Rio Grande do Sul</li>";
    echo "<li>Minas Gerais</li>";
    break;
  case "pessoa":
    echo "<li>Pedro Eugenio Antunes</li>";
    echo "<li>Paulo Salim Maluf</li>";
    break;
  case "outro":
    echo "<li>abc</li>";
    echo "<li>def</li>";
    echo "<li>ghi</li>";
    echo "<li>jkl</li>";
    echo "<li>mno</li>";
    echo "<li>pqr</li>";
    echo "<li>stu</li>";
    echo "<li>vxy</li>";
    echo "<li>wz</li>";
    echo "<li>123</li>";
    echo "<li>456</li>";
    echo "<li>789</li>";
    echo "<li>001</li>";
    echo "<li>002</li>";
    echo "<li>003</li>";
    echo "<li>004</li>";
    echo "<li>005</li>";
    echo "<li>006</li>";
    echo "<li>007</li>";
    echo "<li>008</li>";
    break;
}
echo "</ul>";
?>