pre-commit-php-cs-fixer.sh

#!/bin/bash


# stolen from template file
if git rev-parse --verify HEAD > /dev/null
then
    against=HEAD
else
    # Initial commit: diff against an empty tree object
    against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
fi

# this is the magic:
# retrieve all files in staging area that are added, modified or renamed
# but no deletions etc
FILES=$(git diff-index --name-only --cached --diff-filter=ACMR $against -- | grep php$)

if [ "$FILES" == "" ]; then
    exit 0
fi

echo -n "PHP CS Fixer "

for FILE in $FILES
do
    php vendor/fabpot/php-cs-fixer/php-cs-fixer fix $FILE --config=sf23 --quiet
    echo -n .
done

echo " Done"

You'll need to have done this:
composer require fabpot/php-cs-fixer

And it's currently set to Symfony Framework v2.3 standards/glitter