Core PHP Programming, Third Edition

1.4. How PHP Works with the Web Server

The normal process a Web server goes through to deliver a page to a browser is as follows. It all begins when a browser makes a request for a Web page. Based on the URL, the browser resolves the address of the Web server, identifies the page it would like, and gives any other information the Web server may need. Some of this information is about the browser itself, like its name (Mozilla), its version (4.08), or the operating system (Linux). Other information given the Web server could include text the user typed into form fields.

If the request is for an HTML file, the Web server will simply find the file, tell the browser to expect some HTML text, and then send the contents of the file. The browser gets ...