how to install composer in php code example

Example 1: install composer

php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
php -r "if (hash_file('sha384', 'composer-setup.php') === '795f976fe0ebd8b75f26a6dd68f78fd3453ce79f32ecb33e7fd087d39bfeb978342fb73ac986cd4f54edd0dc902601dc') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"
php composer-setup.php
php -r "unlink('composer-setup.php');"

Example 2: where do you install composer

// Adding permissions after installing Composer on Mac OSX
sudo chmod 755 /usr/local/bin/composer.phar

Example 3: how to install composer windows

why is it so hard to install composer every time it's a struggle