BBCode Helper 2

<?php
if ( ! defined('BASEPATH')) exit('No direct script access allowed');

if ( ! function_exists('bbcode'))
{
    function bbcode($str = '')
    {
        $ci =& get_instance();
        $ci->load->helper('url');
     
        $str = $ci->security->xss_clean($str);
     
        $str = strip_tags($str, '<img>');
        $str = auto_link($str);
        
        $str = nl2br($str);
        
        $find = array(
            "~\[b\](.*?)\[/b\]~is",
            "~\[i\](.*?)\[/i\]~is");
            
        $replace = array(
            '<b>\\1</b>',
            '<i>\\1</i>');
            
        return preg_replace($find, $replace, $str);  
    }
}

Features

**** Bold
** Italic
http://url/ Url
<img src="" alt="" /> Image
\n <br> New lines!

Improve :)