INSTALL Linux, Apache, MySQL, PHP (LAMP) stack on Ubuntu 18.04

sudo apt-get update
sudo apt-get install apache2

sudo apache2ctl configtest
sudo ufw app list
sudo nano /etc/apache2/apache2.conf

Inside, at the bottom of the file, add a ServerName directive, pointing to your primary domain name. If you do not have a domain name associated with your server, you can use your server’s public IP address:

ServerName server_domain_or_IP

Example:- ServerName localhost

Install MySQL

sudo apt-get install mysql-server

Note :- Installation may complete without asking for root password. Then here is the solution for setting root password and secure MySQL –  MySQL Server Installed Without Password For Root user On Ubuntu 17.10 / 18.04

Install PHP

sudo apt install php-pear php-fpm php-dev php-zip php-curl php-xmlrpc php-gd php-mysql php-mbstring php-xml libapache2-mod-php;
sudo apt-get install php-mcrypt;
sudo apt-get install php-cli;
sudo apt-get install php-gd;

sudo systemctl restart apache2
or
sudo /etc/init.d/apache2 restart