$re = '/<yt-formatted-string id=\"subscriber-count\" [^>]+>(.*?)<\/yt-formatted-string>/m';
$str = ' <yt-formatted-string id="subscriber-count" class="style-scope ytd-c4-tabbed-header-renderer">1,94 mln subskrypcji</yt-formatted-string>';
preg_match_all($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