What are the best practices for structuring PHP code when dealing with mathematical functions like binomial coefficients?

When dealing with mathematical functions like binomial coefficients in PHP, it is important to structure your code in a way that is clear, efficient, and reusable. One best practice is to create a separate function specifically for calculating binomial coefficients, keeping the logic isolated and easy to maintain. Additionally, using appropriate variable names and comments can help improve readability and understanding of the code.

function binomialCoefficient($n, $k) {
    if ($k == 0 || $k == $n) {
        return 1;
    } else {
        return binomialCoefficient($n - 1, $k - 1) + binomialCoefficient($n - 1, $k);
    }
}

$n = 5;
$k = 2;
$result = binomialCoefficient($n, $k);
echo "The binomial coefficient of $n choose $k is $result";