What are the best practices for updating PHP scripts to be compatible with newer versions like PHP 8?

When updating PHP scripts to be compatible with newer versions like PHP 8, it is important to review deprecated features, syntax changes, and potential backward incompatibilities. Some best practices include using strict typing, updating function signatures, replacing deprecated functions, and handling errors more explicitly.

// Example of updating function signatures to be compatible with PHP 8

// Before PHP 8
function calculateSum($num1, $num2) {
    return $num1 + $num2;
}

// After PHP 8
function calculateSum(int $num1, int $num2): int {
    return $num1 + $num2;
}