PHP Include Function with example Tutorial

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:


Home -
About Us -
Links -
Contact Us
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:


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.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:


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!



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!
PHP Require Function
Just like the previous lesson, the require function is used to include a file into your PHP code. However there is one huge difference between the two functions, though it might not seem that big of a deal.
Require vs Include
When you include a file with the include function and PHP cannot find it you will see an error message like the following:
PHP Code:

include("noFileExistsHere.php");
echo "Hello World!";
?>
Display:
Warning: main(noFileExistsHere.php): failed to open stream: No such file or directory in /home/websiteName/FolderName/tizagScript.php on line 2 Warning: main(): Failed opening 'noFileExistsHere.php' for inclusion (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/websiteName/FolderName/tizagScript.php on line 2 Hello World!
Notice that our echo statement is still executed, this is because a Warning does not prevent our PHP script from running. On the other hand, if we did the same example but used the require statement we would get something like the following example.
PHP Code:

require("noFileExistsHere.php");
echo "Hello World!";
?>
Display:
Warning: main(noFileExistsHere.php): failed to open stream: No such file or directory in /home/websiteName/FolderName/tizagScript.php on line 2 Fatal error: main(): Failed opening required 'noFileExistsHere.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/websiteName/FolderName/tizagScript.php on line 2
The echo statement was not executed because our script execution died after the require function returned a fatal error! We recommend that you use require instead of include because your scripts should not be executing if necessary files are missing or misnamed.