How to enable the required extensions with commandline access

1. Via Commandline:

      sudo apt-get install libgmp-dev php7.0-gmp curl php7.0-curl
2. Add the line below to the php.ini (e.g. /etc/php7.0/apache2/php.ini) [?]

      extension=gmp.so   
3. Restart your webserver (e.g. Apache):

      sudo service apache2 reload