PHP Include Function

Without understanding much about the details of PHP, you can save yourself a great deal of time with the use of the PHP include function. The include function takes a file name and simply inserts that file’s contents into the script that calls used the include function.

Why is this a cool thing? Well, first of all, this means that you can type up a common header or menu file that you want all your web pages to include. When you add a new page to your site, instead of having to update the links on tens of separate web pages, you can simply change the menu file.

Example

Say we wanted to create a common menu file that all our pages will use. A common practice for naming files that are to be included is to use the “.inc” extension. Since we want to create a common menu let’s save it as “menu.inc”.

menu.inc Code:

Save the above file as “menu.inc”. Now create a new file, “index.php” in the same directory as “menu.inc”. Here we will take advantage of the include function to add our common menu.

index.php Code:
< ?php include("menu.inc"); ?>

This is my home page that uses a common menu to save me time when I add new pages to my website!

Display:
Home - About Us - Links - Contact Us

This is my home page that uses a common menu to save me time when I add new pages to my website!

And we would do the same thing for “about.php”, “links.php”, and “contact.php”. Just think how terrible it would be if you had 15 or more pages with a common menu and you decided to add another web page to that site. You would have to go in an manually edit every single file to add this new page, but with include files you simply have to change “menu.inc” and all your problems are solved. Avoid such troublesome occasions with a simple include file.

What do Visitor’s See?

If we were to use the include function to include a common menu on each of our web pages, what would the visitor see if they viewed the source of “index.php”? Well, because the include function is pretty much the same as copying and pasting, the visitors would see:

View Source of index.php to a Visitor:

The visitor would actually see all the HTML code as one long line of HTML code, because we have not inserted any new line characters. We did some formatting above to make it easier to read. We will be discussing new line characters later.

Recap

The include command simply takes all the text that exists in the specified file and copies it into the file that uses the include function. Include is quite useful when you want to include the same PHP, HTML, or text segment on multiple pages of a website. The include function is used widely by PHP web developers.

The next lesson will talk about a slight variation of the include function: the require function. It is often best to use the require function instead of the include function in your PHP Code. Read the next lesson to find out why!