Answers for "command to install php5.4 in ubuntu 18.04"

install php 7.4 on ubuntu 20.04

sudo apt update
sudo apt install php7.4
sudo apt install php7.4-common php7.4-mysql php7.4-xml php7.4-xmlrpc php7.4-curl php7.4-gd php7.4-imagick php7.4-cli php7.4-dev php7.4-imap php7.4-mbstring php7.4-opcache php7.4-soap php7.4-zip php7.4-intl -y

change php version ubuntu

$ sudo update-alternatives --config php
 or
$ sudo a2enmod php7.1(version)

install php 7.4 ubuntu

sudo apt update
sudo apt install php php-cli php-fpm php-json php-pdo php-mysql php-zip php-gd  php-mbstring php-curl php-xml php-pear php-bcmath

install php 5.6 on ubuntu 18.04

$ sudo add-apt-repository ppa:ondrej/php