PSR-1 and PSR-2 came out of PHP-FIG at the end of last year, and their value is not that four spaces beat a tab. It is that the question stops being a matter of taste in review and becomes a command that either exits zero or does not.
composer require --dev squizlabs/php_codesniffer:~1.4
vendor/bin/phpcs --standard=PSR2 --report=summary application/libraries
# the same findings, as a patch instead of a list
vendor/bin/phpcs --standard=PSR2 --report=diff application/libraries | patch -p0PSR-2 covers braces, indentation, visibility keywords, line length and where a namespace declaration sits — and deliberately says nothing about naming, structure or design, which are the things worth spending review on. Pointing it at an existing tree produces thousands of errors, so the useful first move is not to fix them all: run it over the files in the current change, taken from git diff --name-only, and let the standard spread as the code is touched. The diff report is what makes that cheap, since most of what PSR-2 flags is mechanical enough to apply unread.