In what situations should include() be preferred over require() in PHP scripts, and vice versa, to avoid errors or warnings?

The main difference between include() and require() in PHP is how they handle errors. include() will only produce a warning if the file is not found and continue executing the script, while require() will produce a fatal error and stop the script execution. If the file being included is not crucial for the script to run, include() can be preferred to avoid halting the script. On the other hand, if the included file is essential for the script to function correctly, require() should be used to ensure that any issues with the file are addressed before proceeding.

// Using include() when the included file is not crucial for the script
include('optional_file.php');

// Using require() when the included file is essential for the script
require('essential_file.php');