The relationship carding of Nginx fastcgi php-fpm

CGI (Common Gateway Interface)
The CGI name is a "public Gateway Interface" (Common Gateway Interface), a tool that the HTTP server "chats" with programs on your or other machines, and its programs must be run on a network server.
CGI can be written in any language, as long as the language has standard input, output, and environment variables. such as PHP,PERL,TCL and so on.

FastCGI
FastCGI is like a resident (long-live) CGI, which can be executed all the time, so long as it is activated, it will not take a moment to fork once (this is the most notorious fork-and-execute mode of CGI). It also supports distributed operations where the FastCGI program can execute and accept requests from other Web servers on hosts other than the Web server.
FastCGI is a language-independent, extensible architecture for CGI open extensions whose main behavior is to keep the CGI interpreter process in memory and thus achieve high performance. As we all know, the repeated loading of CGI interpreter is the main reason of poor CGI performance, if the CGI interpreter remains in memory and accepts the FASTCGI process manager scheduling, it can provide good performance, scalability, fail-over characteristics and so on.

PHP-FPM
PHP-FPM is a PHP fastcgi manager that is only for PHP and can be downloaded in http://php-fpm.org/download.
PHP-FPM is actually a patch of PHP source code designed to integrate FASTCGI process management into a PHP package. It must be patch into your PHP source code and can be used after compiling and installing PHP.
Now we can download in the latest PHP 5.3.2 source tree to directly integrate the PHP-FPM branch, it is said that the next version will be fused into the main branch of PHP. Relative SPAWN-FCGI,PHP-FPM in the CPU and memory control are better, and the former is easy to crash, must be monitored with crontab, and PHP-FPM does not have this annoyance.
PHP5.3.3 has integrated php-fpm, no longer a third-party package. PHP-FPM provides a better way to manage the PHP process, can effectively control the memory and process, can be smooth overloaded PHP configuration, more than spawn-fcgi have a bit more, so by the official PHP included. The PHP-FPM can be turned on with the –ENABLE-FPM parameter when the./configure.

nginx+fastcgi Operating principle
Nginx does not support direct invocation or parsing of external programs, and all external programs (including PHP) must be called through the FastCGI interface. The FastCGI interface is a socket under Linux (the socket can be either a file socket or an IP socket). In order to invoke a CGI program, you also need a fastcgi wrapper (wrapper can be understood as the program used to start another program), which is bound to a fixed socket, such as a port or a file socket. When Nginx sends a CGI request to the socket, through the FastCGI interface, wrapper accepts the request and derives a new thread, which invokes the interpreter or the external program to process the script and reads the return data; Wrapper the returned data through the FastCGI interface, along the fixed socket to nginx; Finally, Nginx sends the returned data to the client, which is the whole process of nginx+fastcgi. The detailed process, as shown in:

The relationship carding of Nginx fastcgi php-fpm