install php 7.3 in debian

Thanks to:
https://computingforgeeks.com/how-to-install-php-7-3-on-ubuntu-18-04-ubuntu-16-04-debian/

 sudo apt-get install php7.3-<entension-name>

sudo apt-get install php7.3-fpm  php7.3-curl php7.3-mysql php7.3-xml php7.3-zip php7.3-gd
apt policy php7.3-fpm