user and blog signup at same time on wordpress multisite

I am using wordpress multisite to create blog in my main site. Wordpress multisite allows us to signup for either user or blog, but i need to create a blog and a user at the same time and the user created need to be assigned as the admin of the blog created. Well i created a user and set it as administrator by changing it's metadata (wp_capabilities, wp_user_level) but when i tried to login to the admin of the blog created then it says you don't have sufficient priviledge. Do anyone know what do i missing?

Thanks in advance.

You have to create a custom registration. Create a new page: registration. In the theme folder make a page-registration.php file, and in the file create your form and the registration function, that should go something like this:

if($_POST)
    {

    $data=$_POST;

    $validateuser=wpmu_validate_user_signup($data['user_name'],$data['user_email']);
    $validateblog=wpmu_validate_blog_signup($data['user_name'],$data['blog_title']);

    $usererrors=$validateuser['errors']->errors;
    $blogerrors=$validateblog['errors']->errors;

    if(!$usererrors && !$blogerrors)
    {
        $meta = array ('lang_id' => 1,'public' => 1);
        $meta = apply_filters( 'add_signup_meta', $meta );
        $path='/'.$data['user_name'].'/';
        wpmu_signup_blog($domain,$path,$data['blog_title'],$data['user_name'],$data['user_email'], $meta);
    }
}

note: this is only an example where the new blogname is the same as your username

leave a comment if you need more detailed instructions or have any additional questions