Loading .php file under WordPress plugins function

I have a WordPress plugins script

<?php
/*
Plugin Name: Saswat Routroy
Plugin URI: http://www.maheshchari.com/
Description: Description of my plugin
Author URI: http://www.maheshchari.com/
*/
class new_menu {

    function new_menu()
    {
        add_action('admin_menu', array(&$this, 'my_admin_menu'));
    }

    function my_admin_menu()
    {   //create a main admin panel
        //create a sub admin panel link above
        add_menu_page('CMS', 'CMS', 'administrator', 8, array(&$this,'overview'));
        add_submenu_page(8, 'View CMS Page', 'View CMS Page', 'administrator', 1, array(&$this,'view_page'));
        add_submenu_page(8, 'Add CMS Page', 'Add CMS Page', 'administrator', 2, array(&$this,'add_page'));
        //These functions adds sub menu for different kinds of admin panel on back end
        add_options_page('Pages Options', 'Saswat  Plugin', 'administrator', basename(__file__),array(&$this, 'my_plugin_options'));
        add_posts_page('Pages posts', 'Saswat  Plugin', 'administrator', basename(__file__),array(&$this, 'my_plugin_posts'));
        add_media_page('Pages media', 'Saswat  Plugin', 'administrator', basename(__file__),array(&$this, 'my_plugin_media'));
        add_pages_page('Pages pages', 'Saswat  Plugin', 'administrator', basename(__file__),array(&$this, 'my_plugin_pages'));
        add_users_page('Pages users', 'Saswat  Plugin', 'administrator', basename(__file__),array(&$this, 'my_plugin_users'));
        add_management_page('maheshchari', 'Mahesh  Plugin', 'administrator', basename(__file__),array(&$this, 'my_plugin_tools'));
        add_theme_page('maheshchari', 'Mahesh  Plugin', 'administrator', basename(__file__),array(&$this, 'my_plugin_themes'));

    }


    function overview()
    {
        echo '<h2>My WordPress Plugin Overview</h2>';
    }

    function view_page()
    {
        echo '<h2>My WordPress Plugin Settings</h2>';
    }

    function add_page()
    {
        //echo '<h2>My WordPress Plugin Generel</h2>';
        echo "<form method='POST' action=''>
    <ul>
        <li><label for='fname'>Family Name (Sir Name)<span> *</span>: </label>
        <input id='fname' maxlength='45' size='10' name='fname' value='' /></li>    

        <li><label for='lname'>Last Name<span> *</span>: </label>
        <input id='lname' maxlength='45' size='10' name='lname' value='' /></li>
        <li><label for='lname'>Last Name<span> *</span>: </label>
        <input type='submit' maxlength='45' size='10' name='lname' value='' /></li>
    </ul>
</form>";
    }
    function my_plugin_options()
    {
        echo '<h2>My WordPress Plugin Options</h2>';

    }
    function my_plugin_posts()
    {
        echo '<h2>My WordPress Plugin posts</h2>';
    }
    function my_plugin_media()
    {
        echo '<h2>My WordPress Plugin media</h2>';
    }
    function my_plugin_pages()
    {
        echo '<h2>My WordPress Plugin pages</h2>';
    }
    function my_plugin_users()
    {
        echo '<h2>My WordPress Plugin users</h2>';
    }

    function my_plugin_tools()
    {
        echo '<h2>My WordPress Plugin tools</h2>';
    }

    function my_plugin_themes()
    {
        echo '<h2>My WordPress Plugin themes</h2>';
    }


}


$mybackuper = &new new_menu();//instance of the plugin class

?>

The file is kept under wp-contentpluginsadmin-menunew_menu.php

Now in the function add_page() I am echoing the html. I don’t want to do this, is there way that I can load a .php page under the function without echoing the script.

Say something like

<?php get_template_part( 'content-home' );?>