This list not complete , cURL is now part of PHP and some other extension that mentioned un documented , is documented is PHP manual 2015
These are not actual extensions. They are part of the PHP core and cannot be left out of a PHP binary with compilation options.
These extensions are bundled with PHP.
These extensions are bundled with PHP but in order to compile them, external libraries will be needed.
These extensions are available from » PECL. They may require external libraries. More PECL extensions exist but they are not documented in the PHP manual yet.