$re = '~(.*?)[^/]+/?$~m';
$str = 'https://domain.com/tags/js/
https://domain.com/dir/negotiations/chi
https://domain.com/ask/parent/quest/pr/';
$subst = "\1";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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