Vid Luther has posted a guide for getting the latest version of SSH working as a PHP extension on your Snow Leopard installation.
Getting PHP with SSH support is not an easy task in Snow Leopard. If you need it, here's a hackish way to do it, until Sara or Mike get around to patching the ssh2 in PECL.
You'll need Xcode and Brew to follow along with his example. He shows you how to set things set up (fail the pecl install), patch that failed file with the patch here and make/make install and you should have a nice shared object (.so) you can now install into your PHP instance.