Advanced Sitemap Generator shortcode overhaul

<?php
/*
Plugin Name: Advanced Sitemap Generator
Plugin URI: http://www.csschopper.com/
Description: powerfull plugin to show all your pages and post on front end in a sitemap.
Version: 1.0.3
Author: Deepak Tripathi
Author URI: http://www.csschopper.com/
Author Email: deepak@sparxtechnologies.com
License: GPL
*/


// Hook for adding admin menus
add_action('admin_menu', 'custom_function');

function custom_function()
{
    add_options_page('sitemap', 'sitemap', 'manage_options', 'sitemapgenerator', 'sitemapfunction');
}

function sitemapfunction()
{
    ?>
<div><h2>Sitemap Setting</h2></div>
  <p>This plugin is the most powerfull plugin which easily display you post and page through shortcode on front end.You just need to put shortcode([sitemap]) on your page/post.</p>
      <p>If you want to exclude pages then put ([sitemap excludepage="1,4"]) where 1,4 are the page id seperated by the comma's.</p>
      <p>If you want to exclude categories then put ([sitemap excludepage="1,4" excludecat="6,3"]) where 6,3 are the category id seperated by the comma's.</p>
      <p>If you want to exclude post then put ([sitemap excludepage="1,4" excludecat="6,3" excludepost="1,183"]) where 1,183 are the post id seperated by the comma's.</p>
  </p> </br></br>
   <div>
       <h2>Screenshot1</h2>
  <div><img src="<?php echo plugins_url() ?>/advanced-sitemap-generator/images/screenshot-1.jpg" width="1100"/></div>
   </br><hr></br>
  <h2>Screenshot2</h2>
  <div><img src="<?php echo plugins_url() ?>/advanced-sitemap-generator/images/screenshot-2.jpg" width="1100"/></div>
  </br><hr></br></br>
  </div>

<?php

}
add_shortcode( 'sitemap', 'sitemap_function' );

function sitemap_function($atts)
{
    extract(shortcode_atts(array(
        "excludepage"   => 0,
        "excludecat"    => 0,
        "excludepost"   => 0,
    ), $atts));

    $args=array(
        'exclude'   => $atts[excludepage],
        'title_li'  => '',
        'echo'      => false
    );

    $output =  '<div class="manage-pagepost"><ul class="manage_page"><h3>Pages</h3>';

    $output .= wp_list_pages($args);

    $output .= '</ul><ul class="manage_post"><h3>posts</h3>';

    for($i=0;$i<count($arr);$i++){
        $arr_new[]='-'.$arr[$i];
    }

    $arr=explode(',',$atts[excludecat]);
    $excludecat=implode(',',$arr_new);
    $str=explode(',',$atts[excludepost]);
    $args = array(
        'post_type' => 'post',
        'cat' => $excludecat,
        'post__not_in' => $str
    );

    query_posts($args);
    if (have_posts()) {
        while (have_posts()) { the_post();
            $output .= '<li><a href="'.get_permalink().'">'.get_the_title().'</a></li>';

        } // while have_posts()
    } // if have_posts

    wp_reset_query();
    $output .= '</ul></div>';

    return $output;
}
?>