Zend_Config_Ini_Writer不工作:错误500

我有这段代码来用Zend Framework创建一个config.ini文件，但我总是从网页中获得Internal Server Error (Error 500)。。。

<?php
session_start();
$config = new Zend_Config_Ini('config.ini',null,array('skipExtends' => true, 'allowModifications' => true));
// CREATE VALUE
$config->database = array();
$config->base = array();
$config->system = array();
$config->home = array();
$config->other = array();
    //DATABASE
    $config->database->hostname = $_SESSION['db_hostname'];
    $config->database->username = $_SESSION['db_username'];
    $config->database->password = $_SESSION['db_password'];
    $config->database->port = $_SESSION['db_port'];
    $config->database->database = $_SESSION['db_name'];
    // BASE
    $config->base->base_url = $_SESSION['base_url'];
    $config->base->site_name = $_SESSION['site_name'];
    $config->base->site_slogan = $_SESSION['site_slogan'];
    // SYSTEM
    $config->system->license = 'false';
    $config->system->cms_type = 'free';
    $config->system->system_email = $_SESSION['system_email'];
    // HOME
    $config->home->homepage_type = 'welcome';
    $config->home->blog_limit = 10;
    $config->home->homepage_message = 'Welcome to CustomCMS!';
    // OTHER
    $config->other->copyright_text = 'Copyright &169; 2012 FMarcoux - All rights reserved';
// Write the config file
$writer = new Zend_Config_Writer_Ini(array('config' => $config,'filename' => 'config.ini'));
$writer->write();
// NOW EXECUTE SQL FILE
$sqlErrorText = '';
$sqlErrorCode = 0;
$sqlStmt = '';
$sqlFileToExecute = 'install_query.sql';
$con = mysql_connect($_SESSION['db_hostname'].':'.$_SESSION['db_port'],$_SESSION['db_username'],$_SESSION['db_password']) or die(mysql_error());
mysql_select_db($_SESSION['db_name'], $con) or die();
if ($con)
{
   // Load and explode the sql file
   $f = fopen($sqlFileToExecute,"r+");
   $sqlFile = fread($f,filesize($sqlFileToExecute));
   $sqlArray = explode(';',$sqlFile);
   //Process the sql file by statements
   foreach ($sqlArray as $stmt)
   {
      if (strlen($stmt) > 3)
      {
         $result = mysql_query($stmt);
         if (!$result)
         {
            $sqlErrorCode = mysql_errno();
            $sqlErrorText = mysql_error();
            $sqlStmt      = $stmt;
            break;
         }
      }
   }
   mysql_query("INSERT INTO `users` (`id`, `username`, `password`, `role`, `full_name`, `email`, `avatar`, `avatar_type`, `ip`, `comments`, `bio`, `privacy_level`, `location`, `banned`, `user_slogan`) VALUES (1, 'admin', '".md5($_SESSION['admin_password']."', 3, 'admin', '".$_SESSION['admin_email']."', '', 'none', '127.0.0.1', 0, '', 3, '', 0, '');") or die(mysql_error());
}
if ($sqlErrorCode == 0)
{
    echo "<tr><td>Installation was finished succesfully!</td></tr>";
    header('Location: done.php');
} 
else
{
include('header.php');
?>
<div id="main">
    <h1>Writing File...</h1>
    <hr />
    <?php
    echo "<tr><td>An error occured during installation!</td></tr>";
    echo "<tr><td>Error code: ".$sqlErrorCode."</td></tr>";
    echo "<tr><td>Error text: ".$sqlErrorText."</td></tr>";
    echo "<tr><td>Statement:<br/> ".$sqlStmt."</td></tr>";
    ?>
</div>
<div id="sidebar">
    <ol>
        <li><strike>Welcome</strike></li>
        <li><strike>Database</strike></li>
        <li><strike>Admin</strike></li>
        <li><strike>Basic Configuration</strike></li>
        <li><b>Create 'config.ini'</b></li>
        <li>Done</li>
    </ol>
</div>
<div id="footer"></div>

抱歉代码太长

如果有人能帮我解决这个问题，我将不胜感激！

注意：我的所有$_SESSION[]都已设置