php-fpm fastcgi phpcgi What are these used for?

I often see these things, but I can’t understand the information I checked online. Can anyone explain it in layman’s terms?

Conceptual understanding: CGI, FastCGI, PHP-CGI and PHP-FPM

Better give me a chestnut!

Thank you

Reply content:

I often see these things, but I can’t understand the information I checked online. Can anyone explain it in layman’s terms?

Conceptual understanding: CGI, FastCGI, PHP-CGI and PHP-FPM

Better give me a chestnut!

Thank you

CGI is a set of interface rules, which are used to establish the communication method between the HTTP server and the dynamic handler.
FastCGI can be regarded as an implementation of CGI. It allows one CGI process to handle multiple requests by making the CGI handler resident in the process, reducing the time and resource consumption of repeatedly starting CGI programs.

php-cgi is a FastCGI used to provide PHP program processing.
php-fpm (FastCGI Process Manager) is a management tool for managing FastCGI processes on top of FastCGI programs.
php-cgi is a single process. When a php-cgi is opened to process a request, only one request can be processed at a time, and the remaining requests are queued.
php-fpm manages multiple FastCGI processes so that requests can be sent to multiple FastCGI processes in parallel for processing at the same time.
It can be simply understood as php-fpm manages multiple php-cgi

As a simple example, a request is sent from the client to the Nginx server and then processed by the PHP program:

• The request is sent to the Nginx server, and the Nginx server sends it to php-fpm according to the configuration. However, Nginx and php-fpm are products of two companies. How can they ensure that they can understand the information sent by each other? This is because they all followed the rules of CGI when designing.

• After php-fpm receives the request, it will find an idle process in the FastCGI process it manages to process the request

• In addition, Nginx can also be connected to php-cgi, but php-cgi does not have a process management module, but is a single process.

Refer to Yin Chuan’s answer, the relationship between FastCgi and PHP-fpm