php 5.6 install ubuntu code example
Example 1: install php 7.3 ubuntu
sudo apt install php7.3-cli php7.3-fpm php7.3-json php7.3-pdo php7.3-mysql php7.3-zip php7.3-gd php7.3-mbstring php7.3-curl php7.3-xml php7.3-bcmath php7.3-json
Example 2: install php 5.6 on ubuntu 18.04
$ sudo add-apt-repository ppa:ondrej/php