This is the first of three articles dealing with Server Side Includes, usually called simply SSI. In this article, I'll talk about configuring your server to permit SSI and introduce some basic SSI techniques for adding dynamic content to your existing HTML pages.
In the second article, we'll talk about some of the somewhat more advanced things you can do with SSI, and in the third week, we'll look at the advanced things that can be done with SSI, such as conditional statements in your SSI directives.
SSI (Server Side Includes) are directives that are placed in HTML pages and evaluated on the server while the pages are being served. They let you add dynamically generated content to an existing HTML page, without having to serve the entire page via a CGI program or other dynamic technology.
The decision of when to use SSI, and when to have your page entirely generated by some program, is usually a matter of how much of the page is static and how much needs to be recalculated every time the page is served. SSI is a great way to add small pieces of information, such as the current time. But if a majority of your page is being generated at the time that it is served, you need to look for some other solution.
To permit SSI on your server, you must have the following directive either
httpd.conf file or in a
This tells Apache that you want to permit files to be parsed for SSI directives.
Not just any file is parsed for SSI directives. You have to tell Apache
which files should be parsed. There are two ways to do this. You can tell
Apache to parse any file with a particular file extension, such as
.shtml, with the following directives:
AddType text/html .shtml
AddHandler server-parsed .shtml
One disadvantage to this approach is that if you wanted to add SSI
directives to an existing page, you would have to change the name of that page,
and all links to that page, in order to give it a
extension, so that those directives would be executed.
The other method is to use the
XBitHack tells Apache to parse files for SSI directives if they
have the execute bit set. So, to add SSI directives to an existing page, rather
than having to change the file name, you would just need to make the file
chmod +x pagename.html
A brief comment about what not to do. You'll occasionally see people
recommending that you just tell Apache to parse all
for SSI, so that you don't have to mess with
.shtml file names.
These folks have perhaps not heard about
XBitHack. The thing to
keep in mind is that, by doing this, you're requiring that Apache read through
every single file that it sends out to clients, even if they don't contain any
SSI directives. This can slow things down quite a bit and is not a good idea.
Of course, on Windows, there is no such thing as an execute bit to set, so that limits your options a little if you're running Apache on Windows.
SSI directives have the following syntax:
<!--#element attribute=value attribute=value ... -->