Below is my code, the code generates a user custom options menu page, after adding the sub menu page, when I click the sub menu option, the page refreshes but the sub menu page content is not visible, only the main page content sticks. Please help me to where I am wrong. Do I have to register_setting or any thing else....

<?php
  // create custom plugin settings menu
  add_action('admin_menu', 'omr_create_menu');
  add_action('admin_menu', 'omr_create_submenu');

  function omr_create_menu() {
    //create new top-level menu
    add_menu_page('My Menu Page', 'Main Menu', 'administrator', __FILE__,   'main_menu_page', 'favicon.ico');
  }
?>
<?php 
  function main_menu_page() {
    global $title;
?>
  <h2><?php echo $title;?></h2>
  My New Menu Page!!
<?php
  }

  function omr_create_submenu(){
    add_submenu_page(__FILE__, 'My SubMenu Page', 'My Submenu', 'administrator', 'my_new_submenu', 'my_submenu_page');
  }
  function my_submenu_page() {
    global $title;
?>
  <h2><?php echo $title;?></h2>
  My New Submenu Page!!
<?php
  }
?>

Originally asked by: Solomon Henry on Stack Overflow