Global Composer Setup

composer.sh

#!/usr/bin/env bash
# As root

# Make config and data dirs
mkdir /etc/composer -p || exit 1
mkdir /var/lib/composer -p

# Set composer home dir to global location
cat << EOF > /etc/profile.d/composer.sh
#!/usr/bin/env bash

export COMPOSER_HOME=/etc/composer
export COMPOSER_ALLOW_SUPERUSER=1
EOF
export COMPOSER_HOME=/etc/composer
export COMPOSER_ALLOW_SUPERUSER=1

# Allow dir to be passed when sudoing
# sudo composer global ...
cat << EOF > /etc/sudoers.d/composer
Defaults env_keep += "COMPOSER_HOME"
Defaults env_keep += "COMPOSER_ALLOW_SUPERUSER"
EOF

# install composer
curl -sS https://getcomposer.org/installer | php -d memory_limit=-1 -- --filename=composer --install-dir=/usr/bin || exit 1

# Reset data and cache dirs to be in normal location
composer config -g cache-dir "~/.composer/cache"
composer config -g data-dir "~/.composer"
chmod +r /etc/composer/auth.json
chmod +r /etc/composer/config.json

# Set global dirs for global context
composer global config data-dir /var/lib/composer
composer global config vendor-dir /var/lib/composer/vendor
composer global config bin-dir /usr/bin

# Add script to update composer and global packages on boot
cat << EOF > /var/lib/cloud/scripts/per-boot/composer_update.sh
#!/usr/bin/env bash

. /etc/profile

composer self
composer global update
EOF
chmod u+x /var/lib/cloud/scripts/per-boot/composer_update.sh

composer global require gmo/credstash "^1.0@dev"
composer global require symfony/console "^2.7 || ^3.0"

echo
echo
echo "Relogin to apply env variables"

Definitely solves a lot of headaches when installing globally and trying to use global requires (like plugins) and the .cache goes to some user's home folder.
Just a question.
Why use /usr/bin instead of /usr/local/bin (to adhere to FHS) ?