PHP include

Summary: in this tutorial, you will learn how to include code from a file using the PHP include construct.

Introduction to the PHP include construct

The include construct allows you to load the code from another file into a file. Here’s the syntax of the include construct:

include 'path_to_file';Code language: PHP (php)

In this syntax, you place the path to the file after the include keyword. For example, to load the code from the functions.php file into the index.php file, you can use the following include statement:

<?php 

// index.php file
include 'functions.php';Code language: HTML, XML (xml)

If PHP cannot find the 'functions.php' file in the src directory, it’ll issue a warning. For example:

Warning: include(functions.php): failed to open stream: No such file or directory in ... on line 4
Warning: include(): Failed opening 'functions.php' for inclusion (include_path='\xampp\php\PEAR') in ... on line 4Code language: PHP (php)

When loading the functions.php file, PHP first looks for the functions.php file in the directory specified by the include_path. In this example, it’s '\xampp\php\PEAR'. If PHP can find the functions.php file there, it loads the code from the file.

Otherwise, PHP searches the functions.php file in the directory of the calling script and the current working directory. If PHP can find the functions.php file there, it loads the code. Otherwise, it issues a warning if the file doesn’t exist.

When PHP loads the functions.php file, it actually executes the code inside the functions.php file. For example, if you place the following code in the functions.php file:

<?php

// functions.php

function get_copyright()
{
	return 'Copyright &copy; ' . date('Y') . ' by phptutorial.net. All Rights Reserved!';
}

echo get_copyright();
Code language: HTML, XML (xml)

and include the functions.php in the index.php file, you’ll see the following output when you run the index.php file:

Copyright © 2021 by phptutorial.net. All Rights Reserved!Code language: CSS (css)

This demonstrated that the include construct does make PHP executes code in the functions.php file.

PHP include example

In practice, you’ll often use the include construct to the page elements from a general site design. For example, all pages in your website may have the same header and footer.

To avoid repeating these elements on multiple pages, you can place the code of the header and footer in separate files such as header.php and footer.php and include them on the pages.

Typically, you place the template files like header.php and footer.php in a separate directory. By convention, the name of the include directory is inc:

.
├── index.php
├── functions.php
├── inc
│   ├── footer.php
│   └── header.php
└── public
    ├── css
    │   └── style.css
    └── js
        └── app.jsCode language: CSS (css)

The header.php file contains the code of the header of the page. It has a link to the style.css file located in the public/css directory:

<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="UTF-8" />
		<meta name="viewport" content="width=device-width, initial-scale=1.0" />
		<link rel="stylesheet" href="public/css/style.css">
		<title>PHP include Example</title>
	</head>
	<body>Code language: HTML, XML (xml)

The footer.php file contains the code related to the footer of the page:

<script src="js/app.js"></script>
</body>
</html>Code language: HTML, XML (xml)

In the index.php file, you can include the header.php and footer.php file like this:

<?php include 'inc/header.php'; ?>

<h1>PHP include</h1>
<p>This shows how the PHP include construct works.</p>

<?php include 'inc/footer.php'; ?>Code language: HTML, XML (xml)

If you run the index.php file and view the source code of the page, you’ll also see the code from the header.php and footer.php files:

<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="UTF-8" />
		<meta name="viewport" content="width=device-width, initial-scale=1.0" />
		<link rel="stylesheet" href="public/css/style.css" />
		<title>PHP include Example</title>
	</head>
	<body>
		<h1>PHP include</h1>
		<p>This shows how the PHP include construct works.</p>

		<script src="public/js/app.js"></script>
	</body>
</html>Code language: HTML, XML (xml)

PHP include & variable scopes

When you include a file, all the variables defined in that file inherit the variable scope of the line on which the include occurs.

1) Including outside a function example

For example, the following defines the $title and $content variables in the functions.php:

<?php

// functions.php

$title = 'PHP include';
$content = 'This shows how the PHP include construct works.';Code language: HTML, XML (xml)

When you include the functions.php in the index.php file, the $title and $content variables become the global variables in the index.php file. And you can use them as follows:

<?php include 'inc/header.php'; ?>


<?php include_once 'functions.php'; ?>

<h1><?php echo $title; ?></h1>
<p><?php echo $content; ?></p>


<?php include 'inc/footer.php'; ?>Code language: HTML, XML (xml)

2) Including within a function example

However, if you include a file in a function, the variables from the included file are local to that function. See the following example:

<?php include 'inc/header.php'; ?>
<?php include_once 'functions.php'; ?>

<?php
	function render_article()
	{
		include 'functions.php';

		return "<article>
                    <h1>$title</h1>
                $content
                </article>";
	}

	echo render_article();
?>


<?php include 'inc/footer.php'; ?>Code language: HTML, XML (xml)

In this example, we include the functions.php inside the render_article() function. Therefore, the $title and $content variables from the functions.php are local to the render_function().

It’s important to note that all functions, classes, interfaces, and traits defined in the included file will have a global scope.

Summary

Use the PHP include construct to load code from another script file.

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