This php.ini file is a part of plesk-php pacahge. For example, for PHP 7.0 it is
# rpm -qf /opt/plesk/php/7.0/etc/php.ini
plesk-php70-7.0.24-centos7.17092912.x86_64
So you can just extract this file from corresponding package or just re-install PHP X.X through Plesk installer.