How could the missing MySQL extension required by WordPress be installed?

["Susmita/Rajib" <bkpsusmitaa@gmail.com>]

Dear illustrious leaders and the senior members, Debian-user ML,

I liked the following two papers of Prof. Shri C K Raju:
ajol-file-journals_601_articles_221195_submission_proof_221195-7072-545591-1-10-20220325.pdf
https://www.ajol.info/index.php/ajct/article/download/221195/210502
ajol-file-journals_601_articles_222634_submission_proof_222634-7072-544552-1-10-20220309.pdf
https://www.ajol.info/index.php/ajct/article/download/222634/210050

and I tried to read Prof. Shri C K Raju's  blog pages, say the one at
http://ckraju.net/blog/?p=189

I received a Firefox-esr notice:
"Your PHP installation appears to be missing the MySQL extension which
is required by WordPress."

Searching the internet, I reached the Stack Overflow page with the
partial title:
Your PHP installation appears to be missing the MySQL extension which
is required by WordPress
at:
https://stackoverflow.com/questions/17694568/php-your-php-installation-appears-to-be-missing-the-mysql-extension-which-is-r#22779915

I followed both the first solution and the approved solution. I
searched in synaptic:
mysql-server
php5-mysql
apache

The nearest that are available in Debian Bullseye :
default-mysql-server
default-mysql-server-core
php-mysql
php7.4-mysql
apache2
php-db
along with their dependencies.

I installed them all. Then I tried to follow the instructions:
# sudo /etc/init.d/mysql status
sudo: /etc/init.d/mysql: command not found

# sudo /etc/init.d/mysql start
sudo: /etc/init.d/mysql: command not found

# /etc/init.d/apache2 restart
Restarting apache2 (via systemctl): apache2.service.

The blog pages still fail to load.

Please feel free to advise.

Best wishes,
Rajib
Etc.