The relationship between CGI and fastcgi and PHP-FPM and php-cgi

CGI is a protocol that specifies that the server nginx will send that data to php-cgi

FastCGI can also be said to be an agreement. FastCGI is an improvement in the performance of CGI. FastCGI starts a master, parses the configuration file (php.ini, etc.), initializes the execution environment, and then starts multiple workers, and when the request comes in, master passes it to a worker and waits for the next request.

PHP-FPM is a program that implements the FASTCGI protocol to manage php-cgi (PHP-FPM is the FASTCGI process Manager)

PHP-CGI is a PHP program that explains

At the beginning of this problem I also quite tangled, read the "HTTP authoritative guide" after the feeling clear a lot.

First of all, what does CGI do? CGI is designed to ensure that the data passed by the Web server is in a standard format and facilitates the writer of CGI programs.

Web server, such as Nginx, is simply the publisher of the content. For example, if the request /index.html , then the Web server will go to the file system to find this file, sent to the browser, here is distributed static data. Well, if the request is now /index.php , according to the configuration file, Nginx know that this is not a static file, need to find a PHP parser to deal with, then he will simply handle the request to the PHP parser. What data will the Nginx send to the PHP parser? URL to have it, query string also have to have, post data also have, HTTP header can not be less, good, CGI is to specify what data to pass, in what format to the rear processing the request of the Protocol. Think carefully about where the users you are using in your PHP code come from.

When the Web server receives /index.php this request, it launches the corresponding CGI program, which is the parser for PHP. The PHP parser then parses the php.ini file, initializes the execution environment, then processes the request, and then returns the processed result in a format specified by the CGI, exiting the process. The Web server then returns the results to the browser.

Well, CGI is a protocol, it doesn't matter what the process is. What is that fastcgi? FastCGI is used to improve the performance of CGI programs.

Improve performance, what is the performance problem with CGI programs? "The PHP parser parses the php.ini file, initializes the execution environment," and here it is. The standard CGI performs these steps for each request (no idle fatigue!). Start the process very tired to say! ), so it takes longer to process each time. This is obviously unreasonable! So how did fastcgi do it? First, fastcgi initiates a master, parses the configuration file, initializes the execution environment, and then starts multiple workers. When the request comes in, master passes it to a worker, and then immediately accepts the next request. This avoids duplication of labor, and efficiency is naturally high. And when the worker is not enough, master can pre-boot several workers according to the configuration and so on, of course, the idle worker too much, will also stop some, this improves the performance, also saves the resources. This is FastCGI's management of the process.

What is that php-fpm? is a realization of the FASTCGI program, by the PHP official received.

As we all know, PHP's interpreter is php-cgi. PHP-CGI is just a CGI program, he himself can only parse the request, return the results, will not process management (the emperor, my concubine really do not AH!) So there are some programs that can dispatch php-cgi processes, such as spawn-fcgi separated by LIGHTHTTPD. Well php-fpm is such a thing, after a long period of development, gradually got everyone's approval (to know, in the previous few years everyone complained php-fpm stability is too poor), but also more and more popular.

Well, finally come back to your question.
Online some say that fastcgi is a protocol that PHP-FPM implemented this Protocol

Right.

Some say that PHP-FPM is the manager of the fastcgi process, used to manage the fastcgi process

Right. The management object of PHP-FPM is php-cgi. But it cannot be said that PHP-FPM is the manager of the fastcgi process, because the fastcgi is a protocol, it seems that no such process exists, even if there is php-fpm can not manage him (at least for now). Some say that php-fpm is a patch for the PHP kernel

Used to be right. Because PHP-FPM is not included in the PHP kernel at the beginning, to use this function, we need to find the same version of the source code php-fpm the kernel patch, and then compile. Later, after the PHP kernel integrates php-fpm, it is much easier to use --enalbe-fpm this compilation parameter.

Some said that after modifying the php.ini configuration file, there is no way to smooth the restart, so the birth of PHP-FPM

Yes, after modifying php.ini, the php-cgi process does not have the means to smooth the restart. PHP-FPM This mechanism is the new worker with a new configuration, the already existing workers can rest after processing the hands of the work, through this mechanism to smooth over.

Also say php-cgi is PHP comes with the fastcgi manager, then why do you get a php-fpm out

Wrong. PHP-CGI is just a program that explains PHP scripts.

The relationship between CGI and fastcgi and PHP-FPM and php-cgi