LAMP stands for
LAMP is a popular open-source software stack used to build and deploy web applications, where Linux acts as the operating system, Apache as the web server, MySQL as the database, and PHP as the programming language.
Although PHP and MySQL have been around for a long time, and maybe LAMP has been replaced by MERN or MEAN stacks, but there are thousands of websites that still use this technology. Having a solid understanding of LAMP can help you when encounter once of these websites that still use PHP and MySQL.
PHP is not very fast. MySQL might have scalability issues. But again, maybe companies run their systems on this framework.