PHP的SAPI

摘自：https://en.wikipedia.org/wiki/Server_Application_Programming_Interface。

In computing, Server Application Programming Interface (SAPI) is the direct module interface to web servers such as the Apache HTTP Server, Microsoft IIS, and Oracle iPlanet Web Server.Microsoft also uses the term Internet Server Application Programming Interface (ISAPI), and the defunct Netscape web server used the term Netscape Server Application Programming Interface(NSAPI) for the same purpose.^[1] In other words, SAPI is actually an application programming interface (API) provided by the web server to help other developers in extending the web server capabilities.

As an example, PHP has a direct module interface called SAPI for different web servers;^[2] in case of PHP 5 and Apache 2.0 on Windows, it is provided in form of a DLL file called php5apache2.dll,^[3] which is a module that, among other functions, provides an interface between PHP and the web server, implemented in a form that the server understands. This form is what is known as a SAPI.

There are different kinds of SAPIs for various web server extensions. For example, another two SAPIs for the PHP language are Common Gateway Interface (CGI) and command-line interface(CLI).^[2][4]

上面摘自Laruence 的空间：http://www.laruence.com/2008/08/12/180.html，初步感觉名字他应该是写错了。

参考http://www.php-internals.com/book/?p=chapt02/02-02-00-overview，感觉写的还是不错的。

关键参看下图：

http://www.csdn.net/article/2014-09-26/2821885-exploring-of-the-php-2，这个讲的也很好。

应该翻译为“服务端应用编程接口”。

总结一下，其实就是PHP作为一个整体而言，与外部的接口，主要是PHP和Web Server的接口，PHP和Shell的接口。

与Web Server的接口就是：CGI、Fast-CGI等等；与Shell的接口就是CLI。