The 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 several web pages, you
can simply change the Menu file.
An Include 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 ".php" extension. Since we want to create
a common menu let's save it as "menu.php".
menu.php Code:
<html>
<body>
<a href="http://www.example.com/index.php">Home</a> -
<a href="http://www.example.com/about.php">About Us</a> -
<a href="http://www.example.com/links.php">Links</a> -
<a href="http://www.example.com/contact.php">Contact Us</a> <br />
Save the above file as "menu.php". Now create a new file, "index.php"
in the same directory as "menu.php". Here we will take advantage
of the include function to add our common menu.
index.php Code:
<?php include("menu.php"); ?>
<p>This is my home page that uses a common menu to save me time when I add
new pages to my website!</p>
</body>
</html>
Display:
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 and
manually edit every single file to add this new page, but with
include files you simply have to change "menu.php" and all your
problems are solved. Avoid such troublesome occasions with a
simple include file.
What do Visitors 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:
<html>
<body>
<a href="index.php">Home</a> -
<a href="about.php">About Us</a> -
<a href="links.php">Links</a> -
<a href="contact.php">Contact Us</a> <br />
<p>This is my home page that uses a common menu to save me time when I add
new pages to my website!</p>
</body>
</html>
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.
Include 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!
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