$re = '/Visiting (.*?)[?] Book the \(\.\*\) hotel[.]/';
$str = 'Visiting London? Book the (.*) hotel.';
$subst = "Visiting \1? Book the \1 hotel.";
$result = preg_replace($re, $subst, $str, 1);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php