$re = '/(?<![^\/])t\.me\/(?!.*?joinchat)(?!.*bot$)[a-zA-Z0-9_]{5,32}$/m';
$str = 'https://t.me/group1
https://t.me/group2
https://t.me/botgroup1
https://t.me/groupbot
https://t.me/group_bot
https://t.me/joinchat/xR7tqA43Dg
https://www.google.com/en/blabla';
preg_match_all($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