You can found check problem like this:
curl -s https://getcomposer.org/installer | php — –check
suhosin.executor.include.whitelist = phar

to disable suhosin run:
mkdir /root/bin && curl -sS https://getcomposer.org/installer | php -n — –install-dir=/root/bin
/usr/local/php56/bin/php56 -n /root/bin/composer.phar require league/some_package