Essentially, “require” and “require_once” are directives in PHP to include and evaluate a specific file during the execution of a script.

These components work just like the pieces of a puzzle, joining forces to form a whole picture. Every single piece is essential to reveal the entire image.

So, why ‘once’ and what is the difference between require and require_once? Let’s delve into the details.

PHP require Keyword

When you use the require statement, PHP essentially imports the content of the specified file at the exact location where the require statement is placed.

This process ensures that the code in the external file becomes an integral part of the main script. It’s like assembling a jigsaw puzzle, where each piece (external file) contributes to the overall picture (your PHP program).

One key advantage of using require over alternatives like include is that it treats file inclusions as mandatory.

In case PHP faces a problem, like not finding or accessing the designated file, it stops executing the program and shows a fatal error. This implies that any issues in including the file can abruptly halt the program.

This behavior is beneficial because it helps you catch and address issues promptly, preventing the program from continuing with incomplete or incorrect dependencies.

Here is an example:

<?php require( "incs/bootstrap.php" ); ?>

To avoid errors when including files, let’s understand how require_once works in the following section.

PHP require_once Keyword

This modifier ensures that the file is included and required only once. Imagine you have a function or a class defined in a file, and you use require_once to include it. If, for some reason, that file is encountered again in your code, PHP won’t try to include it a second time, avoiding conflicts and errors.

By using this statement, you can create modular and reusable code. For example, if you possess a collection of functions used by various scripts, you can organize them in a distinct file. Subsequently, you can include this file wherever necessary using the “require_once” statement in PHP.

Additionally, error handling is another advantage. In case, the file you want to include is not there. In these situations, PHP gives a serious error, stopping your script. This helps you know about problems early so you can fix them fast.

Let’s look at an example in the code below.

<?php require_once( "incs/bootstrap.php" ); ?>

By executing this code, PHP instructs the interpreter to include the bootstrap functions into the current script for one time.

Let’s understand the differences between “require_once” and “require” in PHP.

The Differences Between require_once and require in PHP

Both the require and require_once statements serve the purpose of including external files into your script, but they differ in their approach and implications. Let’s explore the distinctions between the two.

Firstly, the require statement is a way to bring in a file. It’s often used when you want to add code from outside sources into your PHP script. When you use require PHP, reads and adds the chosen file right where the statement is. If there’s an issue finding the file or including it, PHP will make a serious error, and the script will stop running.

When you opt for require_once to bring in a file, PHP checks if the file is already included elsewhere in the script. If it is, PHP skips adding it again, preventing duplicate code execution. This is handy in situations where multiple files might accidentally try to include the same file, sidestepping redundancy and potential conflicts.

It’s crucial to understand that, unlike require which can lead to multiple inclusions of the same file if not handled carefully, require_once ensures a file is included only once, no matter how many times the statement appears. This proves especially beneficial in more extensive projects where maintaining modularization and organized code is paramount.

Wrapping Up

The require_once ensures that crucial files are included only once, preventing confusion or disorder. While the require keyword serves the purpose of including external files in your PHP code, it’s important to manage it cautiously to avoid multiple inclusions of the same external file.

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