Why require_once() Is Not Recommended in Large PHP Projects

Introduction

As a mainstream server-side language, PHP's file inclusion methods significantly affect project structure and performance. The require_once() function is commonly used to include files while preventing multiple inclusions. However, in certain situations, require_once() may not be the best choice. This article will explore why.

Basic Usage of require_once()

The require_once() function includes a specified file during script execution and ensures that the file is included only once to avoid errors caused by redefinitions.

require_once('file.php');

Issues with require_once()

Performance Concerns

Each call to require_once() triggers a file search and loading process. In large projects with many calls, this can cause noticeable performance overhead and increase server load.

To address this, it is recommended to use autoloading mechanisms like spl_autoload_register(), which automatically load class files on demand, reducing unnecessary file searches and improving performance.

spl_autoload_register(function ($class) {
    require_once 'classes/' . $class . '.php';
});

Namespace Conflict Issues

When using namespaces, require_once() may not effectively handle conflicts caused by classes or functions with the same name, potentially resulting in loading errors.

Using autoloaders compliant with the PSR-4 standard can automatically map namespaces to file paths, avoiding conflicts and enhancing code clarity and organization.

spl_autoload_register(function ($class) {
    $file = str_replace('\\', DIRECTORY_SEPARATOR, $class) . '.php';
    require_once $file;
});

Code Readability Issues

Having numerous scattered require_once() statements can make code cluttered and harder to read, especially when many files need to be included, which complicates maintenance.

Centralizing file inclusions or using autoloading to manage all class loading uniformly improves code simplicity and maintainability.

// autoload.php
require_once 'classes/ClassA.php';
require_once 'classes/ClassB.php';
require_once 'classes/ClassC.php';
// ...

Conclusion

While require_once() remains suitable for small projects or simple scripts, its drawbacks regarding performance, namespace conflicts, and readability limit its use in larger projects.

Developers should choose more efficient and standardized autoloading mechanisms such as spl_autoload_register() and PSR-4 to achieve better code quality and execution efficiency according to project scale and needs.