What best practices should be followed when updating PHP code for long-standing websites to ensure compatibility with newer versions?

When updating PHP code for long-standing websites to ensure compatibility with newer versions, it is important to review deprecated functions and features that may no longer be supported. It is also recommended to update any outdated syntax or configuration settings to align with the latest PHP standards. Additionally, testing the updated code thoroughly on a development environment before deploying it to the live website is crucial to identify and address any compatibility issues.

// Example code snippet to update deprecated function mysql_connect to mysqli_connect
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

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

// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}
echo "Connected successfully";