An Introduction to Server Side Includes
Beginner? That's OK!
While much has been written about Server Side Includes (SSIs -also known as Virtual Includes) much of this information is designed for intermediate to advanced webmasters. This article is aimed at beginners. It is assumed that the reader has no prior knowledge of scripting languages, servers, or any other advanced computer skills. This article will introduce the reader to SSIs and explain how they are used in web site development. SSIs are guaranteed to save you time as your web site develops and changes over time.
Servers: just a place for your stuff?
It is important to understand that all the code for your website is stored remotely on a computer called a server. On a very basic level, the server (remote computer) is just a place where you can store the files on the "net." These files would typically contain your web site's HTML code and possibly some files containing pictures or graphics.
For example, a very simple web site might consist of 5 web pages with five corresponding files that are stored on the server. One file is named index.html and we will have four additional files. These files might be named about-me.html , education.html , resume.html , and portfolio.html. We'll say that this simple 5 page web site is run by a freelancer who uses this site as a kind of virtual advertisement.
Servers Part 2: more than storage?
We have established that the server functions as a storage place for our files, but it is important to recognize servers can also do things. Similar to the operating systems software on our personal computers, servers have software that allows them to access and organize files. Servers can also carry out more advanced functions. Take, for example, what the server does when someone visits the root directory of your site; the server automatically loads your index page (e.g., index.html, index.php, index.asp). This is a very simple example of something that happens on the "server side."
Why do I need includes?
Now that we understand that remote servers have software on them capable of carrying out certain tasks, we can turn our attention to the "includes" portion of the equation. What are includes? Let's take our hypothetical web site that serves as an advertisement for our imaginary freelancer. Imagine that the freelancer designs a left hand navigation menu so that people can easily browse all five pages of his site. Therefore, each page of this site contains the code for the navigation bar. Imagine that a few months after launching this web site, our freelancer wants to add a Frequently Asked Questions page. Our freelancer now has to update the navigation bar code in each of his five existing pages. Now there are six pages with this same navigation bar code. A month later our freelancer wants to add a self-written article to his site. Once again every page on the site needs to be updated. Imagine having a site with 100's of pages. Do you want to manually update 100's of pages of code? These are the types of situations where virtual includes can save you hours of time.
What are we including on the server side?
Perhaps it would be better to think of includes as "modules" that we can insert into our web pages. These modules (or "includes") are usually just text files that contain HTML code (although they can be other file formats). The code inside these files can be inserted anywhere in a page simply by using an include command. For example, imagine for a moment that our freelancer had the foresight to realize that the navigation menu would change at some point in the future. Instead of putting the code for the navigation menu into each individual page, the freelancer placed this code into a separate file. For the sake of example, we can call this file nav-menu.html Our freelancer can now simply place an "include" command that refers to the nav-menu.html anywhere he/she wants to place this menu. The advantage of this is becomes apparent when our freelancer needs to modify the navigation menu. Just one file needs to be edited, nav-menu.html, and all the pages containing "include" refering to this file will automatically update themselves. This time savings is the primary advantage of using includes.
OK, I get it, but what does an include look like?
Even though this is not a "technical" article, many of you are probably wondering what an "include" looks like. Therefore, one example for PHP is included below. Please note PHP is just one type of scripting language that can be used, depending on what your server is running. In this example, the code contained in the file "nav-menu.html" will be inserted into any web page where the following code is placed:
Keep in mind that, for technical reasons, server side includes will never be visible when you view the source code for a page in your browser. This is because the include happens on the server (before presenting the resulting code to the browser). This makes the use of SSIs invisible to browsers, bots, spiders (which is why they are search engine friendly)
The catch-22 of server side includes is that the need for them only becomes apparent when faced with the task of updating tens or hundreds of pages of code. There are many resources on the web that will instruct you how use virtual includes, and procedures will vary depending on the type of scripting language supported by your server (e.g., ASP, PHP). Hopefully you now understand Server Side Includes and how they can benefit the webmaster.
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