Create PHP file in joomla 1.5

<?php

define( 'DS', DIRECTORY_SEPARATOR );
$rootFolder = explode(DS,dirname(__FILE__));

//current level in  directory structure 
//example : (components/com_banner/view/tpl/   >>> $currentfolderlevel = 4;)

$currentfolderlevel = 4;

array_splice($rootFolder,-$currentfolderlevel);

$base_folder = implode(DS,$rootFolder);


if(is_dir($base_folder.DS.'libraries'.DS.'joomla'))
{

define( '_JEXEC', 1 );

define(JPATH_BASE,implode(DS,$rootFolder));

require_once ( JPATH_BASE .DS.'includes'.DS.'defines.php' );
require_once ( JPATH_BASE .DS.'includes'.DS.'framework.php' );
$userid='';
$usertype='';
$mainframe =& JFactory::getApplication('site');
$mainframe->initialise();
$user =& JFactory::getUser();
$userid = $user->get('id');
$usertype = $user->get('usertype');
}
?>