How to set different users for different pages?

Question

Create a subfolder in plugins folder, name it ‘MyRestict’. In This folder put the following php:

<?php 
/**
 * Plugin Name: My Restict
 * Plugin URI: http://wordpress.stackexchange.com/questions/112566/how-to-set-different-users-for-different-pages
 * Author: G.M.
 */

function my_restict_template_filter( $template ) {
  if ( is_page() ) {
    $post = get_queried_object();
    $allowed = (string) get_post_meta($post->ID, 'allowed_users', true);
    if ( $allowed ) $allowed = array_map('trim', explode(',', $allowed) );
    $user = wp_get_current_user();
    if ( ! empty($allowed) && ( ! is_object($user) || ! in_array($user->ID, $allowed) ) )
      return plugin_dir_path(__FILE__) . 'not-allowed.php';
  }
  return $template;
}

add_filter('template_include', 'my_restict_template_filter');

In the same ‘MyRestict’ folder create a file named not-allowed.php and there put something like:
```
<div>Sorry, you are not allowed to view this page.</div>
```
In your pages you have to create a custom field with the key allowed_users where you have to write comma separed list of users ids of users that you want to allow viewing that page:
Activate the ‘My Restict’ plugin in the backend

Remember that pages that do not have any custom field will be accessible to all visitors, even not logged ones.