PHP Include and Require

PHP allows you to insert the content of one PHP file into another using include and require. This promotes code reuse and keeps your project organized.

include vs require

The key difference: if the file is not found, include produces a warning and continues execution, while require produces a fatal error and stops execution.

include and require

<?php
// include — warning if file missing, script continues
include 'header.php';
include 'nav.php';

// require — fatal error if file missing, script stops
require 'config.php';   // critical — must exist
require 'database.php'; // critical — must exist

// include_once / require_once — prevent duplicate inclusion
include_once 'functions.php';
require_once 'classes/User.php';

echo "Page content here";

include 'footer.php';
?>

Practical Example — Shared Header & Footer

A common use case is splitting a page into reusable parts: header, navigation, content, and footer.

Shared Layout Files

<!-- header.php -->
<?php
$siteName = "My Website";
?>
<!DOCTYPE html>
<html>
<head>
    <title><?php echo $siteName; ?></title>
</head>
<body>
<header><h1><?php echo $siteName; ?></h1></header>

Using Shared Files

<?php
require_once 'includes/header.php';
require_once 'includes/nav.php';
?>

<main>
    <h2>Welcome to the Home Page</h2>
    <p>This is the main content area.</p>
</main>

<?php
require_once 'includes/footer.php';
?>

<!-- config.php — loaded once, shared across all pages -->
<?php
// config.php
define('DB_HOST', 'localhost');
define('DB_NAME', 'myapp');
define('DB_USER', 'root');
define('DB_PASS', 'secret');
define('BASE_URL', 'https://example.com/');
?>

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PHP Include and Require

include vs require

Practical Example — Shared Header & Footer

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