Using mod_php as a DSO (legacy)
This method is the oldest and slowest possible configuration. It was suitable for version 2.2 and older, and requires the use of the prefork mpm.
Why you shouldn't use mod_php with the prefork mpm anymore
mod_php is loaded into every httpd process all the time. Even when httpd is serving static/non php content, that memory is in use.
mod_php is not thread safe and forces you to stick with the prefork mpm (multi process, no threads), which is the slowest possible configuration