PHP Include File
Server Side Includes (SSI) are used to create functions, headers,
footers, or elements that will be reused on multiple pages.
Server Side Includes
You can insert the content of a file into a PHP file before the server
executes it, with the include() or require() function. The two functions are
identical in every way, except how they handle errors. The include() function
generates a warning (but the script will continue execution) while the require()
function generates a fatal error (and the script execution will stop after the
error).
These two functions are used to
create functions, headers, footers, or elements that can be reused on multiple
pages.
This can save the developer a considerable amount of time. This means that
you can create a standard header or menu file that you want all your web pages
to include. When the header needs to be updated, you can only
update this one include file, or when you add a new page to your site, you can simply change the
menu file (instead of updating the links on all web pages).
The include() Function
The include() function takes all the text in a specified file and copies it
into the file that uses the include function.
Example 1
Assume that you have a standard header file, called "header.php". To include
the header file in a page, use the include() function, like this:
<html>
<body>
<?php include("header.php"); ?>
<h1>Welcome to my home page</h1>
<p>Some text</p>
</body>
</html>
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Example 2
Now, let's assume we have a standard menu file that should be used on all
pages (include files usually have a ".php"
extension). Look at the "menu.php" file below:
<html>
<body>
<a href="http://www.w3schools.com/default.php">Home</a> |
<a href="http://www.w3schools.com/about.php">About Us</a> |
<a href="http://www.w3schools.com/contact.php">Contact Us</a>
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The three files, "default.php", "about.php", and "contact.php"
should all include the "menu.php" file.
Here is the code in "default.php":
<?php include("menu.php"); ?>
<h1>Welcome to my home page</h1>
<p>Some text</p>
</body>
</html>
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If you look at the source code of the "default.php" in a browser, it will look something like
this:
<html>
<body>
<a href="default.php">Home</a> |
<a href="about.php">About Us</a> |
<a href="contact.php">Contact Us</a>
<h1>Welcome to my home page</h1>
<p>Some text</p>
</body>
</html>
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And, of course, we would have to do the same thing for "about.php" and "contact.php".
By using include files, you simply have to update the text in the "menu.php"
file if you decide to rename or change the order of the links or add another web page to the site.
The require() Function
The require() function is identical to include(), except that it handles
errors differently.
The include() function generates a warning (but the script will continue
execution) while the require() function generates a fatal error (and the script
execution will stop after the error).
If you include a file with the include() function and an error occurs, you
might get an error message like the one below.
PHP code:
<html>
<body>
<?php
include("wrongFile.php");
echo "Hello World!";
?>
</body>
</html>
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Error message:
Warning: include(wrongFile.php) [function.include]:
failed to open stream:
No such file or directory in C:\home\website\test.php on line 5
Warning: include() [function.include]:
Failed opening 'wrongFile.php' for inclusion
(include_path='.;C:\php5\pear')
in C:\home\website\test.php on line 5
Hello World!
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Notice that the echo statement is still executed! This is because a Warning
does not stop the script execution.
Now, let's run the same example with the require() function.
PHP code:
<html>
<body>
<?php
require("wrongFile.php");
echo "Hello World!";
?>
</body>
</html>
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Error message:
Warning: require(wrongFile.php) [function.require]:
failed to open stream:
No such file or directory in C:\home\website\test.php on line 5
Fatal error: require() [function.require]:
Failed opening required 'wrongFile.php'
(include_path='.;C:\php5\pear')
in C:\home\website\test.php on line 5
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The echo statement was not executed because the script execution stopped
after the fatal error.
It is recommended to use the require() function instead of include(), because
scripts should not continue executing if files are missing or misnamed.
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