require vs. include vs. require_once vs. include_once in PHP: What's the Difference?

Understanding the Differences Between require, include, require_once, and include_once in PHP

When working with PHP, it's essential to understand the distinctions between various file inclusion directives. This article sheds light on the key differences between require vs. include and require_once vs. include_once.

When to Use require vs. include

The require() function behaves similarly to include(), but its error handling differs. If an error occurs during the require() call, it triggers a fatal error and halts the script execution. On the other hand, the include() function produces a warning but allows the script to continue.

When to Use require_once vs. require/include_once

The require_once() and include_once() directives are similar to their counterparts, require() and include(). The primary difference is that these "once" variants perform an additional check before including the file. PHP determines if the file has been included previously and, if so, it skips the inclusion.

Deprecation of *_once Variants

It's important to note that the *_once variants have become somewhat obsolete in modern PHP development. They may have been used in the past due to habit or to prevent potential cascading errors. However, it's generally recommended to restructure code and rely on other mechanisms for ensuring file inclusion only once.

The above is the detailed content of require vs. include vs. require_once vs. include_once in PHP: What's the Difference?. For more information, please follow other related articles on the PHP Chinese website!