What are Server Side Includes?

Server Side Includes (SSIs) are directives, embedded in your html document as comments, that are executed by the web server. The results of each directive is included, in-line, in the document returned to your browser. Example:
<!--#flastmod virtual="rtmf.shtml"-->
  Would return something like:  
Tuesday, 14-Apr-1998 10:54:05 British Summer Time
  There are six basic SSI directives and Apache eXtented SSIs (XSSI) adds two additional directives plus conditional execution of SSI directives.

Why use SSIs

There are several advantages to using SSIs in your html documents.
  • You can use SSIs to include a standard header, footer and/or navigation information in your web documents. If you at some later date want to change the layout or navigation of your site, you alter the header, footer, or navigation files and all your documents will then be served with your new style. All the pages in the Apache RTFM use a standard header and footer.
  • You can incorporate the results of a program in your document.
  • In many cases, SSIs can be quicker to implement that CGI programs.

There are several disadvantages to using SSIs

  • Like CGIs, SSIs can potentially create a security breach in your web server. Any command which is available to a general user on you operating system could be included in as an SSI.
  • SSIs increase the load on your server. When SSIs are enabled for a file, Apache must read the entire file looking for SSI directives and execute them.
  • You have to learn something new! This may be the greatest deterrent to you using SSIs.

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Apache RTFM last updated Saturday October 21 2006