In cases where PHP code needs to be updated or rewritten, what steps should be taken to ensure a smooth transition and minimize disruptions to website functionality?

When updating or rewriting PHP code, it is important to first thoroughly test the changes in a development environment to catch any potential issues before deploying them to the live website. It is also recommended to create a backup of the current codebase to revert back to in case of any unforeseen problems. Additionally, documenting the changes made and ensuring that all dependencies are updated can help minimize disruptions to website functionality.

// Example PHP code snippet for updating a function to use a more efficient algorithm
function calculate_sum($numbers) {
    $sum = 0;
    foreach ($numbers as $number) {
        $sum += $number;
    }
    return $sum;
}

// Updated function using array_sum() for a more concise and efficient calculation
function calculate_sum($numbers) {
    return array_sum($numbers);
}