Use random string in permastructure

/**
 * Random string in permastructure
 * Use %random% in "Permastructure" settings
 */
function pm_random_string_field($default_uri, $native_slug, $post, $slug, $native_uri) {
    // Do not affect native URIs
    if($native_uri == true || empty($post->post_type)) { return $default_uri; }

    if(strpos($default_uri, '%random%') !== false) {
        $chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
        $length = 12;
        $random_string = substr(str_shuffle($chars), 0, $length);

        $default_uri = str_replace('%random%', $random_string, $default_uri);
    }

    return $default_uri;
}
add_filter('permalink_manager_filter_default_post_uri', 'pm_random_string_field', 3, 5);