There is no stable release of PHP-Sat (yet). Check the
road map for the current status of the 0.1 release.
You can always download, install and try the latest version that was successfully build.
Subversion
The latest distributions contain the latest of the latest developments, but if you really want to, the latest sources can be checked out using:
svn checkout https://svn.strategoxt.org/repos/psat/php-sat/trunk
Before you can configure the package using
./configure --enable-bootstrap you have to run the
./bootstrap script.