$re = '/^(?!\d+\s*$)\d+.+$/m';
$str = 'Here goes some text. {tag} A wonderful day. It\'s soon cristmas.
2 Happy 2019, soon. {Some useful tag!} Something else goes here.
3 Happy ending. Yeppe! See you.
4
5 Happy KKK!
6 Happy B-Day!
7
8 Universe is cool!
9
10 {Tagish}.
11
12 {Slugish}. Here goes another line. {Slugish} since this is a new sentence.
13
14 endline.
4 ';
preg_match_all($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