WordPress add a new page to admin section

Question

I have already developed my plugin for WordPress and I can manage it from admin. I have passed the access to the plugin file using add_submenu_page. The problem is that the plugin is extending and I want to use another file that is linked from the main file. For example I have second_page.php?id=3. When I try to access this link, I get a

You do not have sufficient permissions to access this page.

message. I want to "validate" this page also for using with this script and I don't know how. Ideas?

Answer 1

When you add a page with add_submenu_page(), the url should be something like:

wp-admin/admin.php?page=<your_page_handle>

Your page is actually loaded from admin.php (typically). You can add parameters to your links by appending something like &id=3 and then have your main plugin page-loading logic determine which file to include based on the parameter.

For instance

if (isset($_GET['id']) && ((int) $_GET['id']) == 3) {
  include 'second_page.php';
} else {
  include 'first_page.php';
}

Edit:

I found a trick that may be easier for you, though I haven't thoroughly tested it. Let's say that you have two pages: my_one and my_two. Just call add_submenu_page twice, and set the second page's parent as the first page. This will cause Wordpress to not add a link to the navigation bar, but you can still access your page by navigating to admin.php?page=my_two.

Example:

    add_submenu_page( 
          'my_toplevel_link'   
        , 'Page Title'
        , 'Link Name'
        , 'administrator'
        , 'my_one' // here's the page handle for page one
        , 'my_one_callback'
    );
    add_submenu_page( 
          'my_one'  // set the parent to your first page and it wont appear
        , 'Page Title'
        , 'Link Name'  // unused
        , 'administrator'
        , 'my_two'
        , 'my_two_callback'
    );