Require and Include in PHP

PHP include() Function

The include() function in PHP works like the require() function because it lets you add and run an external PHP file within your current script. But, there are some important differences in how include() deals with errors and how it adds the files.

When the include() function is encountered, it includes the specified file & continues executing the script even if the file is not found or contains errors. If an error occurs, a warning is generated, but the script continues running.

The include() function is typically used when the included file is not critical to the script's functionality, & you want to allow the script to continue executing even if the file is missing or contains errors.

Syntax

The syntax for the include() function is :

include 'filename.php';

Again, 'filename.php' represents the path to the PHP file you want to include, which can be absolute or relative to the current script's directory.

Example

Now, let's take an example to show the use of the include() function. Suppose we have two files: main.php & footer.php.

main.php:

<?php
echo "<h1>Welcome to my website!</h1>";
include 'footer.php';
?>

footer.php:

<footer>
    <p>&copy; 2023 My Website. All rights reserved.</p>
</footer>
</body>
</html>

In this example, the main.php script displays the "Welcome to my website!" heading & then uses the include() function to include the footer.php file. The footer.php file contains the HTML structure for the page footer.

If the footer.php file is not found or contains errors, a warning will be generated, but the script will continue executing, displaying the heading from main.php. This behavior allows for more flexibility in handling non-critical file inclusions.

Advantages of include() in PHP

1. Flexibility: include() allows the script to continue executing even if the included file is not found or contains errors, providing more flexibility in handling non-critical file inclusions.
 

2. Error handling: If the file specified in include() is not found or contains errors, a warning is generated, but the script continues running, allowing you to handle errors more gracefully.
 

3. Code organization: Like require(), include() helps in organizing code into separate files, making it easier to manage and maintain larger projects.
 

4. Code reusability: include() promotes code reusability by allowing you to include common code snippets in multiple scripts, reducing duplication and improving maintainability.
 

5. Dynamic file inclusion: include() can be used with variable file names, enabling dynamic file inclusion based on runtime conditions or user input.

6. Performance: While include() is slightly slower than require() due to its error handling behavior, it still provides a way to include external files efficiently.
 

7. Conditional inclusion: include() can be combined with conditional statements to include files based on specific conditions, providing more control over the inclusion process.

Difference between require() and include() Functions

Frequently Asked Questions

What happens if the file specified in require() is not found?

If the file specified in require() is not found, the script will terminate with a fatal error, and the rest of the script will not be executed.

Can I use variables in the file path for include() and require()?

Yes, you can use variables to specify the file path in both include() and require() functions, allowing for dynamic file inclusion based on runtime conditions or user input.

Is it possible to include the same file multiple times using include() or require()?

Yes, it is possible to include the same file multiple times using include(). However, with require(), the file will be included only once, even if the require() statement is called multiple times.

Conclusion

In this article, we have learned about the require() and include() functions in PHP, which are used to include and execute external PHP files within a script. We discussed their syntax, examples, and the important differences between them. require() is used for including critical files and terminates the script if an error occurs, while include() is used for including non-critical files and continues executing the script even if an error occurs. Both functions help in organizing code, promoting reusability, and improving maintainability.
You can also check out our other blogs on Code360.