How PHP Works with the Web Server PHP

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 the contents and begins rendering the page based on the HTML code. If you have been programming HTML for any length of time, this will be clear to you.

Hopefully you have also had some experience with CGI scripts. When a Web server gets a request for a CGI, it can't just send the contents of the file. It must execute the script first. The script will generate some HTML code, which then gets sent to the browser. As far as the browser is concerned, it's just getting HTML. The Web server does a bunch of work that it gets very little recognition for,but Web servers rarely get the respect they deserve. The medium is definitely not the message.

When a PHP page is requested, it is processed exactly like a CGI, at least to the extent that the script is not simply sent to the browser. It is first passed through the PHP engine,which gives the Web server HTML text.

What happens when the user clicks the stop button before the page finishes downloading? The Web server detects this situation and usually terminates the PHP script. It is possible to force a script to finish despite an aborted connection. You may also allow the script to terminate but execute special code first.



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