- Curl Fetching files by HTTP.
- XMLWriter For formatting XML and HTML output.
-- mysqlnd The native driver for PHP5 MySQL/MariaDB connections.
+- mysqlnd The native driver for PHP5 MariaDB connections. If you
+ use MySQL, 'mysql' or 'mysqli' may work.
- GD Image manipulation (scaling).
- mbstring For handling Unicode (UTF-8) encoded strings.
- bcmath or gmp For Salmon signatures (part of OStatus)