regex to match utf8 hashtags (similar to Instagram and Facebook)

regex-match-utf8-hashtags.php

/**
 * @see https://regexr.com/4suqt
 * @see https://regex101.com/r/4SAxik/1
 * @see https://www.regexpal.com/?fam=113956
 **/

$regex = "(?:#)([\p{L}\p{N}_](?:(?:[\p{L}\p{N}_]|(?:\.(?!\.))){0,28}(?:[\p{L}\p{N}_]))?)";

$text = "here is a #hashtag.tail and #another_hashtag #هشتگ #__hehe #123 this is a test.";

preg_match_all($regex, $text, $matches);

var_dump($matches);

you can split regex like below:

$alphabets = '\p{L}\p{N}_';
$sign = '#';
$regex = "/(?:$sign)([$alphabets](?:(?:[$alphabets]|(?:\.(?!\.))){0,28}(?:[$alphabets]))?)/u";

can be used for mentions (change $sign to @) too.