title: set_include_path function does not work, PHP 5.2.13
body: <p>We are using a VPS server in our company and I'm trying to install Roundcube webmail interface</p>
  
  <p>But I can't even get to the configuration phase because the set_include_path function doesn't work and the script can't find the required configuration files.</p>
  
  <p>I get an error like "Fatal Error, ini_set/set_include_path function does not work."</p>
  
  <p>I assume some php settings is causing this but I don't which one.</p>
  
  <p>I'd be glad if I could get some help.</p>
  
  <p>Thanks in advance</p>
  
  <p><strong>//EDIT</strong>  Here is the codes from the script</p>
  
  <pre><code>ini_set('error_reporting', E_ALL&amp;~E_NOTICE);
  ini_set('display_errors', 1);
  
  define('INSTALL_PATH', realpath(dirname(__FILE__) . '/../').'/');
  define('RCMAIL_CONFIG_DIR', INSTALL_PATH . 'config');
  
  $include_path  = INSTALL_PATH . 'program/lib' . PATH_SEPARATOR;
  $include_path .= INSTALL_PATH . 'program' . PATH_SEPARATOR;
  $include_path .= INSTALL_PATH . 'program/include' . PATH_SEPARATOR;
  $include_path .= ini_get('include_path');
  
  set_include_path($include_path);
  
  require_once 'utils.php';
  require_once 'main.inc';
  </code></pre>