How does Apache or Nginx work together with PHP: What is the difference between mod_php5, php-cgi and php-fpm?

How Apache or Nginx works together with PHP: In-depth discussion of mod_php5, php-cgi, and php-fpm

As web servers, Apache and Nginx cannot directly process PHP code. The execution of PHP code requires middleware, and mod_php5, php-cgi and php-fpm play this role. They are not mutually substitute, but different ways to achieve the same goal.

We can liken them to different means of transportation: mod_php5 is like a built-in car, php-cgi is like a bus, and php-fpm is like an efficient cab fleet. They all deliver you to your destination (processing PHP requests and returning results), but there are different efficiency and flexibility.

mod_php5: It is a module of Apache that is directly embedded in Apache. After Apache receives the PHP request, it directly calls mod_php5 for processing, which is efficient but has poor flexibility. The stability of Apache is closely related to PHP.

php-cgi: This is a standalone CGI program that communicates with Apache or Nginx through the CGI protocol. Each request requires starting a new php-cgi process, which is flexible but relatively inefficient.

php-fpm (FastCGI Process Manager): php-fpm manages multiple php-cgi processes, avoiding the overhead of starting a new process every time you request and significantly improving efficiency. It is usually used with Nginx for better performance and stability.

In summary, the web server (Apache or Nginx) receives HTTP requests and forwards the request to the PHP interpreter (mod_php5, php-cgi or php-fpm). After the PHP interpreter processes the code, it returns the result to the server and finally presents it to the user. Which method to choose depends on project requirements and performance requirements. Currently, the combination of php-fpm with Nginx is widely considered a best practice.

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