[Editor's note: unless you have special demands, use the appropriate deps package from <http://windows.php.net/downloads/php-sdk/>.]
SSH2 for Windows is not available from the authors of the extension. But compiled binaries are available from the Apache Lounge (which is recommended by the php.net website too).
Link for PHP 5.3, 5.4, 5.5, 5.6 and 7.0:
https://www.apachelounge.com/viewtopic.php?t=6359
This binaries contain a lot (maybe even all?) for Windows compiled PHP extensions, like the SSH2 extension.
Please note that it is also highly recommended to use their Windows binary builds for the Apache HTTP server from here: https://www.apachelounge.com/download/
Older versions can be choosen from the left menu (VC11, VC10, etc.) if required.
php.net also recommends to use the binary builds from the Apache Lounge.
Maybe this helps developers, who work with Windows and can't find or compile some extensions themself.