Including PHP files is a way to modularize your code and reuse functions, classes, or variables across multiple PHP files. It's commonly used for separating logic into manageable chunks and promoting code reusability.
The include (or require) statement takes all the text/code/markup that exists in the specified file and copies it into the file that uses the include statement.
In PHP, include and require are statements used to include and evaluate external PHP files within another PHP file. The main difference between them lies in how they handle errors:
include :If the file specified in the include statement is not found or there's an error during inclusion, PHP will issue a warning but continue executing the script.require: If the file specified in the require statement is not found or there's an error during inclusion, PHP will issue a fatal error and stop script execution.
So, if you want the execution to go on and show users the output, even if the include file is missing, use the include statement. Otherwise, in case of FrameWork, CMS, or a complex PHP application coding, always use the require statement to include a key file to the flow of execution. This will help avoid compromising your application's security and integrity, just in-case one key file is accidentally missing.
Including files saves a lot of work. This means that you can create a standard header, footer, or menu file for all your web pages. Then, when the header needs to be updated, you can only update the header include file.
Assume we have a standard footer file called "footer.php", that looks like this:
<?php
echo "<p>Copyright © 1999-" . date("Y") . " Q3Schools.com</p>";
?>
To include the footer file in a page, use the include statement:
<html>
<body>
<h1>Welcome to my home page!</h1>
<p>Some text.</p>
<p>Some more text.</p>
<?php include 'footer.php';?>
</body>
</html>