Using Server-Side Includes (SSI)

NOTE: This document is provided as-is by Texas.Net. SSIs are in no way supported by technical support or the Texas.Net helpdesk. Because SSIs require that the server be configured to parse through .html files, the ability to use SSIs may be removed at any time without warning.

Basics Of SSIs
Before we get to the examples, it'd be first helpful to know what an SSI looks like. SSIs always take the form:

When they appear in your code, they are completely replaced by whatever the server outputs (whether it be text from another HTML page or output from code or the result of a variable evaluation), so you won't be able to tell if their in your source code simply by viewing that code from your browser. When an SSI fails, you will see the line:

Sometimes, however, it may be hidden, especially if the output was supposed to generate part of a table, in which case, nothing would appear. The important thing to remember when using SSIs is that they must all be one line. You can't have line breaks separating the various portions of an SSI or it will simply be outputted to the browser that way (they won't appear in the browser though because they look like comments).

Displaying the "Last Modified" Date
To let your viewers know the last time you updated your web page, you can have the server print out the LAST_MODIFIED server variable. For example, this document was last updated Thursday, 03-Jun-2004 16:36:28 CDT. The line of HTML that produced this value is:

You can put this line anywhere, although most people usually put this in the header or footer of the document. It's great for letting people know when you've last updated your web page.

A Consistent Look
When designing a site of many pages, you might want to make them all look alike, with a common opening header or some such. The Lonestar site is like this, where each page in a section has the same general look and feel of the other pages in that section. Rather than writing the same 70-100 lines of HTML code for the beginning of each page, we create a single document with a generic name like TOP.html and then use that document in all of our web pages with a line like:

This line will take the text from TOP.html and insert it wherever that SSI appears in our code, effectively transferring that entire block of HTML into our web page. With this, you can quickly create a site of numerous pages having, possibly, the same complex interface without hours of complex coding per page.

Variable Interpolation
In addition to LAST_MODIFIED, you can print out other variable values that Apache provides (DATE_GMT, DATE_LOCAL, DOCUMENT_NAME, and DOCUMENT_URI) as well as all of the environment variables and their values. Listed below are the environment variables and their current values.