How many operating modes does PHP have?

Running mode: 1. CGI protocol mode, the server communicates with the program through a specific protocol; 2. "fast-cgi" protocol mode, which can always process requests after it is turned on; 3. Module mode, receives requests and calls "mod_php "Module processing; 4. "php-cli" mode, enter "php xx.php" to execute the code.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

1: CGI protocol mode

cgi mode Common Gateway Interface (Common Gateway Interface), which allows web servers to communicate with applications through specific protocols. In layman’s terms, CGI is like a bridge that connects web pages and executable programs in the WEB server. When connected, it passes the instructions received by HTML to the server execution program, and then returns the server execution program to the HTML page. CGI has excellent cross-platform performance and can be implemented on almost any operating system.
The calling principle is roughly: User request->Web server receives request->fork sub-process calling program/execution program->Program returns content/Program call ends->Web server receives Content->Return to the user. Since each user request has to fork to create a process, call the program once, and then destroy the process, so the performance is low.

2: fast-cgi protocol mode

fast-cgi is an upgraded version of cgi mode, it is like A resident cgi, as long as it is turned on, will not have to spend time forking every time. It can always process requests and no longer need to end the process.
The calling principle is probably : initialization of the web server fast-cgi process manager ->pre-fork n process user requests ->web server receives the request->hand to fast-cgi process management The server->fast-cgi process management area receives it and processes it with one of the idle fast-cgi processes->The processing is completed, the fast-cgi process becomes idle and waits for the next request->The web server receives the content-> Return to user.

3: Module mode

When apache php is running, the module mode is used by default. It uses php as an apache module and starts it when apache starts. The request is processed directly by calling the mod_php module.

The module mode is integrated in the form of mod_php5 module. At this time, the function of mod_php5 module is to receive PHP file requests passed by Apache, process these requests, and then return the processed results to Apache. If we configure the PHP module (mod_php5) in its configuration file before Apache starts, the PHP module registers the ap_hook_post_config hook of apache2 and starts this module when Apache starts to accept requests for PHP files.

Four: php-cli mode

php-cli mode belongs to the command line mode, which is suitable for many developers who just started learning php and started wamp and wnmp. The most unfamiliar operating mode. This mode does not require the use of other programs. You can directly enter php xx.php to execute the php code. The obvious difference between the command line mode and the regular web mode is:

• There is no timeout period
• Buffer buffering is turned off by default
• Use of STDIN and STDOUT standard input/output/error
• echo var_dump, phpinfo and other outputs are directly output to the console
• Usable classes/ Different functions
• Differences in php.ini configuration

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