Types of Dynamic Content

Dynamic content comes in several different forms. A traditional static web server delivers the same file in response to every incoming data request. A dynamic site need not respond in this way, though. Instead, a client's request for a page causes the server to process data in some way. Two common types of dynamic content are:

CGI Scripts The Common Gateway Interface (CGI) is a means of enabling the web server to run an outside program to generate a web page, rather than directly deliver an unchanging web page. The program in question is frequently a script, so these programs are often called CGI scripts. In principle, the external program could be written in a compiled language such as C, Pascal, or FORTRAN, though. In practice, Perl is a very popular CGI scripting language.

SSIs Compared to CGI scripts, Server Side Includes (SSIs) are very primitive. This mechanism enables the web server to modify a template of a web page. You might use this feature to change the date on an otherwise static web page, for example. This chapter doesn't describe SSIs in more detail, but you should be aware of their existence.

Another dynamic content element is important: web forms. These are web pages that include text-entry fields, buttons, selection lists, and so on. Most dynamic content relies on web forms to enable users to enter information to be delivered to the web server for use in generating dynamic content. For instance, a web search engine includes, at a minimum, a text entry field and a button to initiate a search. Like other web pages, web forms are created using HTML. Effective use of GCI scripts requires some knowledge of web forms.

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