Install Composer

"Composer is a tool for dependency management in PHP. It allows you to declare the libraries your project depends on and it will manage (install/update) them for you." - getcomposer.org

Installation

$ php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
$ php -r "if (hash_file('sha384', 'composer-setup.php') === '55ce33d7678c5a611085589f1f3ddf8b3c52d662cd01d4ba75c0ee0459970c2200a51f492d557530c71c15d8dba01eae') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"
$ php composer-setup.php
$ php -r "unlink('composer-setup.php');"

Move to your local bin

sudo mv composer.phar /usr/local/bin/composer

Create an alias to use XAMPP's PHP in your .zshrc

$ vi ~/.zshrc
$ alias composer="/Applications/XAMPP/xamppfiles/bin/php /usr/local/bin/composer"