$re = '/\d+(?:\.\d+)*[\s\S]*?\w+\./';
$str = ' 1 One without dot. 2. Some Random String. 3.1 With SubItens. 3.2 With Another SubItem. 4. List item. 11.12 More than one digit.';
preg_match_all($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