SSI - Software
A server-side include is a variable value (for example, a file "Last modified" date) that a server can include in an HTML file before it sends it to the requestor. If you're creating a Web page, you can insert an include statement in the HTML file that looks like this:
Monday, 24-Jul-2000 11:31:36 EDT
and the server will obtain the last-modified date for the file and insert it before the HTML file is sent to requestors.
LAST_MODIFIED is one of several environment variables that an operating system can keep track of and that can be accessible to a server program. The server administrator can make these environment variables usable when the system is set up.
A Web file that contains server-side include statements (such as the "echo" statement above) is usually defined by the administrator to be a file with an "." suffix. You can think of a server-side include as a limited form of common gateway interface application. In fact, the CGI is not used. The server simply searches the server-side include file for CGI environment variables, and inserts the variable information in the places in the file where the "include" statements have been inserted.)