PHP

Server Side Includes

You can insert the content of one PHP file into another PHP file before the server executes it, with include or require. The two are identical in every way except how they handle errors:

• include (or include_once) generates a warning, but the script continues execution.
• require (or require_once) generates a fatal error, and the script stops.

These statements are used to put functions, headers, footers or other elements that are reused on many pages into separate files. Server side includes save a lot of work: you create a standard header, footer or menu file once for all your web pages. When the header needs to be updated you change only the include file; when you add a new page to your site you change only the menu file instead of the links on every page.

The include Statement

include takes all the content of the specified file and includes it in the current file. If an error occurs, it generates a warning and the script continues.

Assume that you have a standard header file called header.php:

<div style="background:#173b6c;color:#fff;padding:6px">
  <b>PHP Training Institute</b> – Bhopal
</div>

To include the header file in a page, use include:

<html>
<body>
<?php include "header.php"; ?>
<h1>Welcome to my home page!</h1>
<p>Some text.</p>
</body>
</html>

PHP Training Institute – Bhopal
Welcome to my home page!

Some text.

A common menu file

Assume we have a standard menu file, menu.php, that should be used on all pages:

<a href="default.php">Home</a> |
<a href="tutorials.php">Tutorials</a> |
<a href="references.php">References</a> |
<a href="examples.php">Examples</a> |
<a href="about.php">About Us</a> |
<a href="contact.php">Contact Us</a>

All pages of the web site include this menu file:

<html>
<body style="font-family:Arial;font-size:13px">
<div class="leftmenu">
<?php include "menu.php"; ?>
</div>
<h1>Welcome to my home page.</h1>
<p>Some text.</p>
</body>
</html>

OUTPUT browser · http://localhost/phpbook/ch13/page.php

Home | Tutorials | References | Examples | About Us | Contact Us
Welcome to my home page.

Some text.

If you look at the source code of the page in the browser (View Source), the menu file's content appears where the include statement was – the visitor cannot tell that it came from another file:

<html>
<body style="font-family:Arial;font-size:13px">
<div class="leftmenu">
<a href="default.php">Home</a> |
<a href="tutorials.php">Tutorials</a> |
...
<a href="contact.php">Contact Us</a>
</div>
<h1>Welcome to my home page.</h1>
<p>Some text.</p>
</body>
</html>

The require Statement

require is identical to include, except that it handles errors differently: if an error occurs, include produces a warning and the script continues, while require produces a fatal error and the script stops.

Error example – include

<html>
<body>
<?php
include "wrongFile.php";
echo "Hello World!";
?>
</body>
</html>

Warning: include(wrongFile.php): Failed to open stream: No such file or directory in /opt/lampp/htdocs/phpbook/ch13/test_include.php on line 4

Warning: include(): Failed opening 'wrongFile.php' for inclusion (include_path='.:/usr/share/php') in /opt/lampp/htdocs/phpbook/ch13/test_include.php on line 4
Hello World!

Notice that the echo statement is executed, because a warning does not stop the script.

Error example – require

Now let us run the same example with require:

<html>
<body>
<?php
require "wrongFile.php";
echo "Hello World!";
?>
</body>
</html>

Warning: require(wrongFile.php): Failed to open stream: No such file or directory in /opt/lampp/htdocs/phpbook/ch13/test_require.php on line 4

Fatal error: Uncaught Error: Failed opening required 'wrongFile.php' (include_path='.:/usr/share/php') in /opt/lampp/htdocs/phpbook/ch13/test_require.php:4 Stack trace: #0 {main} thrown in /opt/lampp/htdocs/phpbook/ch13/test_require.php on line 4

The echo statement is not executed, because script execution stopped after the fatal error.

include_once and require_once

include_once and require_once behave like include and require, but if the file has already been included they do not include it again. This prevents errors such as "Cannot redeclare function" when a library is included from several places.

<?php
function rupees($amount)
{
    return "Rs. " . number_format($amount, 2);
}

<?php
require_once "functions.php";
require_once "functions.php";   // ignored – already loaded
echo rupees(1250) . "<br>";
echo "Included files:<br>";
foreach (get_included_files() as $f) {
    echo basename($f) . "<br>";
}
?>

Rs. 1,250.00
Included files:
once.php
functions.php

Including Files that Return Values

An included file can return a value. This is a neat way to keep configuration in its own file:

<?php
return [
    'site'   => 'PHP Training Institute',
    'db'     => 'phpbook',
    'perpage'=> 10,
];

<?php
$config = require "config.php";
echo "Site: {$config['site']}<br>";
echo "Database: {$config['db']}<br>";
echo "Records per page: {$config['perpage']}";
?>

Site: PHP Training Institute
Database: phpbook
Records per page: 10

A Complete Page Layout

Most PHP web sites split each page into a header, the page content and a footer:

<!DOCTYPE html>
<html><head><title><?= $title ?? 'My Site' ?></title></head>
<body style="font-family:Arial;font-size:13px">
<div style="background:#173b6c;color:#fff;padding:6px"><b>My Site</b></div>

<div style="border-top:1px solid #999;margin-top:10px;font-size:11px">
  &copy; <?= date("Y") ?> My Site. All rights reserved.
</div>
</body></html>

<?php
$title = "About Us";
require "layout_header.php";
?>
<h2>About Us</h2>
<p>We teach PHP and MySQLi with hands-on projects.</p>
<?php require "layout_footer.php"; ?>

OUTPUT browser · http://localhost/phpbook/ch13/about.php