The Project | About Us | Contribute | Donations | License

HOME

In this section, we will explore two essential functions in PHP: include and require. These functions allow you to include the content of one PHP file into another, which is particularly useful for reusing code, such as headers, footers, or configuration files.

Key Concepts

Include: The include statement includes and evaluates the specified file. If the file is not found, a warning is issued, but the script continues to execute.
Require: The require statement includes and evaluates the specified file. If the file is not found, a fatal error is issued, and the script stops executing.
Include Once and Require Once: These variations ensure that the file is included only once, preventing issues with multiple inclusions.

Syntax

Include

include 'filename.php';

Require

require 'filename.php';

Include Once

include_once 'filename.php';

Require Once

require_once 'filename.php';

Practical Examples

Example 1: Using Include

Let's create a simple example where we include a header file in our main script.

header.php

<!DOCTYPE html>
<html>
<head>
    <title>My Website</title>
</head>
<body>
    <header>
        <h1>Welcome to My Website</h1>
    </header>

main.php

<?php
include 'header.php';
?>
<main>
    <p>This is the main content of the page.</p>
</main>
</body>
</html>

Example 2: Using Require

Now, let's use require to include a configuration file.

config.php

<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "my_database";
?>

main.php

<?php
require 'config.php';

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully";
?>

Example 3: Using Include Once

Using include_once ensures that the file is included only once, even if the statement is called multiple times.

header.php

<!DOCTYPE html>
<html>
<head>
    <title>My Website</title>
</head>
<body>
    <header>
        <h1>Welcome to My Website</h1>
    </header>

main.php

<?php
include_once 'header.php';
include_once 'header.php'; // This will not include the file again
?>
<main>
    <p>This is the main content of the page.</p>
</main>
</body>
</html>

Example 4: Using Require Once

Using require_once ensures that the file is required only once, even if the statement is called multiple times.

config.php

<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "my_database";
?>

main.php

<?php
require_once 'config.php';
require_once 'config.php'; // This will not require the file again

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully";
?>

Practical Exercises

Exercise 1: Include a Footer

Create a footer.php file and include it in your main script.

footer.php

<footer>
    <p>&copy; 2023 My Website</p>
</footer>
</body>
</html>

main.php

<?php
include 'header.php';
?>
<main>
    <p>This is the main content of the page.</p>
</main>
<?php
include 'footer.php';
?>

Solution: Ensure that the footer.php file is correctly included at the end of the main.php file.

Exercise 2: Require a Configuration File

Create a config.php file with database connection details and require it in your main script.

config.php

<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "my_database";
?>

main.php

<?php
require 'config.php';

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully";
?>

Solution: Ensure that the config.php file is correctly required in the main.php file and that the database connection is established successfully.

Common Mistakes and Tips

File Path Errors: Ensure that the file paths are correct. Relative paths are often used, but absolute paths can also be specified.
Using Include vs. Require: Use require for critical files that the application cannot run without, such as configuration files. Use include for optional files, such as templates.
Multiple Inclusions: Use include_once and require_once to prevent multiple inclusions of the same file, which can cause errors or unexpected behavior.

Conclusion

In this section, we learned how to use include and require to include files in PHP. We also explored the variations include_once and require_once to prevent multiple inclusions. These functions are essential for organizing and reusing code in your PHP projects. In the next module, we will dive into control structures, starting with conditional statements.

PHP Include and Require

Key Concepts

Syntax

Include

Require

Include Once

Require Once

Practical Examples

Example 1: Using Include

Example 2: Using Require

Example 3: Using Include Once

Example 4: Using Require Once

Practical Exercises

Exercise 1: Include a Footer

Exercise 2: Require a Configuration File

Common Mistakes and Tips

Conclusion

PHP Programming Course

Module 1: Introduction to PHP

Module 2: Control Structures

Module 3: Functions

Module 4: Arrays

Module 5: Working with Forms

Module 6: Working with Files

Module 7: Object-Oriented Programming (OOP)

Module 8: Working with Databases

Module 9: Advanced PHP Techniques

Module 10: PHP Frameworks and Best Practices

Module 11: Project: Building a Web Application