$re = '/\b(?:abc|def)\s+rules\s+(\d*\.*?\d+(?:(?:,|\s*and)\s*\d*\.*?\d+)*)/';
$str = 'abc rules 2.3, 4.5, 6.7, 8.9 and def rules 3.6, 6.7, 8.9 and 10.11.';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
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