Following commands will add you the CodeSniffer pear package and set it to check for the PSR standards before committing anything to your git repository. No need to what the previous acronyms are about (expect pear and git :) ).
Just do the following:
# pear install PHP_CodeSniffer
# cd /usr/share/pear/PHP/CodeSniffer/Standards/
# git clone http://github.com/klaussilveira/phpcs-psr PSR
Note: The CodeSniffer directory may vary for your system.
$ cd /path/to/your/project/.git/hooks/
$ wget http://raw.github.com/dmtrs/git-hooks/master/phpcs-pre-commit/pre-commit