Wordpress DB transfer

<?php

define('WP_USE_THEMES', false);

require('./wp-config.php');

$old_prefix = 'wp_';

global $wpdb;
$wpdb->query( "UPDATE `$wpdb->usermeta`
    SET `meta_key` = REPLACE( `meta_key` , '$old_prefix', '$wpdb->prefix' )
    WHERE `meta_key` LIKE '" . addcslashes( $old_prefix, '_' ) . "%'" );

$wpdb->query( "UPDATE `$wpdb->options`
    SET `option_name` = '{$wpdb->prefix}user_roles'
    WHERE `option_name` = '{$old_prefix}user_roles' AND `blog_id` = 0" );