What is Server Side Include (SSI) Pages?
A SSI, server side include page is dependent upon software on your server to call each of your include pages into the page when requested by a web browser. An example of a server side include technique is to use PHP (Hypertext Preprocessor) to provide your page file - complete with any include pages within it - to the browser. When viewing a page using PHP server side include pages to provide some of the components of the page the end result displayed to the user is identical to the same page with the component hard-coded on it (rather than provided by the common include file). In fact, if you view the source of the page even the html code displayed would suggest that the component being provided by the include page is actually hard coded on the page.
For example - a common website might have four main regions or components to its design. The header, navigation, body and a footer. In most cases, the header, navigation and footer are identical from page to page - with only the body content changing, dependent upon the given topic of the page. Thus, it would make sense to utilize include pages for each component that is to remain the same from page to page. By using include pages there is only one instance of the code for each of these components. This ensures consistency across each page, and makes it much faster to make a change to any of these regions (as you only have to make the change to the one include file). There are numerous advantages though in using include pages rather than frames, including some advantages in achieving rankings in the search engines as well as some aesthetic and compatibility considerations in using frames.
Two of the widely used SSI besides CGI are PHP and ASP technologies.
What is PHP?
Self-referentially short for PHP: Hypertext Preprocessor, an open source, server-side, HTML embedded scripting language used to create dynamic Web pages. In an HTML document, PHP script (similar syntax to that of Perl or C ) is enclosed within special PHP tags.
PHP pages have the extension .php (in some cases .php3 or .php4 ) instead of .htm, when a page with the extension .asp is requested by a browser the web server knows to interpret any PHP contained within the web page before sending the HTML produced to the browser.
Because PHP is embedded within tags, the author can jump between HTML and PHP (similar to ASP and Cold Fusion) instead of having to rely on heavy amounts of code to output HTML. And, because PHP is executed on the server, the client cannot view the PHP code. PHP can perform any task that any CGI program can do, but its strength lies in its compatibility with many types of databases. PHP can talk across networks using IMAP, SNMP, NNTP, POP3, or HTTP. PHP was created sometime in 1994 by Rasmus Lerdorf. During mid 1997.
What is ASP?
As ASP was first introduced by Microsoft on it's web server, Internet Information Server (IIS), that runs on Windows 2000/XP Pro/NT4, it is this web server that ASP pages usually run best on. ASP pages have the extension .asp instead of .htm, when a page with the extension .asp is requested by a browser the web server knows to interpret any ASP contained within the web page before sending the HTML produced to the browser.
This way all the ASP is run on the web server and no ASP will ever be passed to the web browser. Any web pages containing ASP cannot be run by just simply opening the page in a web browser. The page must be requested through a web server that supports ASP, this is why ASP stands for Active Server Pages, no server, no active pages.
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