PHP upgrade from 7.2 to 7.4 on Ubuntu with Nignx

Take Backup/Snapshot

Always before any upgrade, take a snapshot of the VM.

Spin a new VM from the snapshot if you are not sure of the upgrade

Login to the VM

SSH to the VM instance of Wordpress

Add PHP repository

Ubuntu 18.04 only ships php 7.2 in the default repository. apt-get will not install php 7.4. So first add the repository manually

sudo add-apt-repository ppa:ondrej/php

Update and upgrade the repository

sudo apt update
sudo apt upgrade

Install PHP 7.4

Install Php 7.4 and related extensions

apt-get install php7.4 php7.4-cli php7.4-fpm php7.4-mysql php7.4-json php7.4-opcache php7.4-mbstring php7.4-xml php7.4-gd php7.4-curl

Check Php version. Should get 7.4

$ php -v
PHP 7.4.22 (cli) (built: Jul 30 2021 13:07:59) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
    with Zend OPcache v7.4.22, Copyright (c), by Zend Technologies

Install fpm for NGINX

sudo apt install php7.4-fpm

Configure fpm in the sites

edit the server block files under sites available

/etc/nginx/sites-available$ sudo vim kaykaribasket.lmnas.com

Edit the fpm from 7.2 to 7.4 like below

fastcgi_pass unix:/run/php/php7.4-fpm.sock;

Check Niginx config, Restart Nginx, Restart fpm

$ sudo nignx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
$ sudo service nginx restart
$ sudo service php7.4-fpm restart

Note: To Switch php version use below command

sudo update-alternatives --config php

Finally check the website if it works fine