Simple process run the script step by step in your cmd
php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
php -r "if (hash_file('sha384', 'composer-setup.php') ===
'48e3236262b34d30969dca3c37281b3b4bbe3221bda826ac6a9a62d6444cdb0dcd0615698a5cbe587c3f0fe57a54d8f5')
{ echo 'Installer verified'; } else
{ echo 'Installer corrupt'; unlink('composer-setup.php');
}
echo PHP_EOL;"
php composer-setup.php
php -r "unlink('composer-setup.php');" 