How can I prevent the admin to create a new custom post type more than one?

Question

I am making a plugin that allows admin to create custom post but I want admin to be able to create only one custom post type.

I tried this following to remove "Add New" from admin menu:

function remove_submenus() {
    $count= wp_count_posts('post_type')->publish;
    if( $count>=1 ){
        global $submenu;
        unset($submenu['edit.php?post_type=post_type'][10]);
    }else{} 
}
add_action('admin_menu', 'remove_submenus');

It removes "Add New" item from the menu but user (admin) is still be able to create new custom post type by using this URL (/post-new.php?post_type=post_type).

How can I prevent user to create post more than one?

Answer 1

1. Get the total number of custom types.
2. If the total number of custom type is equal to 1 then throw an error message.

And put that custom post type making process in if else block.

if ($cpt_count == 1) {
  // Create new custom post type
} else {
  // Error
}