//check that site or user theme exists

function theme_exists($theme) {

    ///////////////////////////////////////////////////////////////////////////////////////

    if(isset($_COOKIE['themeswitcher_theme']))        $theme=$_COOKIE['themeswitcher_theme'];

    ///////////////////////////////////////////////////////////////////////////////////////

    if (!file_exists(THEMES) || !is_dir(THEMES)) {

        return false;   

    } else if (file_exists(THEMES.$theme."/theme.php") && file_exists(THEMES.$theme."/styles.css")) {

        define("THEME", THEMES.$theme."/");

        return true;

    } else {

        $dh = opendir(THEMES);

        while (false !== ($entry = readdir($dh))) {

            if ($entry != "." && $entry != ".." && is_dir(THEMES.$entry)) {

                if (file_exists(THEMES.$entry."/theme.php") && file_exists(THEMES.$entry."/styles.css")) {

                    define("THEME", THEMES.$entry."/");

                    return true;

                    exit;

                }

            }

        }

        closedir($dh);

        if (!defined("THEME")) {

            return false;

        }

    }

}