Sync roles between different WordPress Blog inside the same schema on first login

wp_sync_roles.php

<?php
/**
 * Sync roles between different WordPress Blog
 *
 * Tables must be inside the same schema and you have to define 
 * custom user tables on wp-config.php in the SLAVE blog as follow:
 + define('CUSTOM_USER_TABLE', 'myprefix_users');
 + define('CUSTOM_USER_META_TABLE', 'myprefix_usermeta');
 * Sync is run only at the first login on the alternative blog, any following
 * role change must be manually sync.
 * If blogs shares the same main domain (ex. domain.it - blog.domain.it) you can 
 * share logon cookies adding the following to wp-config.php:
 + $root_host = 'epilbeauty.it';
 + define( 'COOKIE_DOMAIN', '.'.$root_host );
 + define( 'COOKIEHASH', md5('http://'.$root_host) );
 *
 * @param String $alt_table_prefix Alternative blog table prefix (ex. 'myprefix_')
 */
function wp_sync_roles_with( $alt_table_prefix ) {
	global $wpdb;

	// Get current user id
	$uid = get_current_user_id();

	// if user not logged or role already been set (save a query) exit
	if (!$uid || current_user_can('read')) return;

	// Get role on current blog
	$role = $wpdb->get_var("SELECT meta_value FROM {$wpdb->usermeta} WHERE meta_key = '".$wpdb->get_blog_prefix()."capabilities' AND user_id = {$uid}");

	// If a role is already set (non default capabilities) exit
	if ($role) return;

	// Get the role in the alternative blog
	$newrole = $wpdb->get_var("SELECT meta_value FROM {$wpdb->usermeta} WHERE meta_key = '{$alt_table_prefix}capabilities' AND user_id = {$uid}");
	$rarr = unserialize($newrole);
	$roles = is_array($rarr) ? array_keys($rarr) : array('non-user');
	$newrole = $roles[0];
	
	// Set new role on current blog
	$wp_user_object = new WP_User($uid);
	$wp_user_object->add_role( $newrole );

	// Page must be reloaded now
	wp_safe_redirect($_SERVER['REQUEST_URI']);
	exit;
}

wp_sync_roles_with('f7sr6w_');