public function pregQuote($user_agent, $delimiter = '/')
{
$pattern = preg_quote($user_agent, $delimiter);
// the \\x replacement is a fix for "Der gro\xdfe BilderSauger 2.00u" user agent match
return str_replace(['\\*', '\\?', '\\x'], ['.*', '.', '\\\\x'], $pattern);
}