In what situations should die() be used in PHP scripts to handle errors, and how can it affect the flow of the script execution?

die() should be used in PHP scripts to handle critical errors that need to stop the script execution immediately. It can be used when encountering database connection failures, missing required files, or other fatal errors. However, die() should be used sparingly as it abruptly terminates the script and may not provide a user-friendly error message.

// Example of using die() to handle a database connection error
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

$conn = mysqli_connect($servername, $username, $password, $dbname);

if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

// Rest of the script continues here if the connection is successful