How do you divide design and calculation steps in PHP projects?

When working on PHP projects, it's important to separate the design and calculation steps to maintain code organization and readability. Design steps involve defining the structure, layout, and user interface elements, while calculation steps involve processing data, performing operations, and executing logic. By dividing these steps, you can easily manage and update different aspects of your project without causing conflicts or confusion.

// Design steps
function displayHeader() {
    // Code to display header design
}

function displayFooter() {
    // Code to display footer design
}

// Calculation steps
function calculateTotal($price, $quantity) {
    return $price * $quantity;
}

function processOrder($total) {
    // Code to process order logic
}

// Example usage
displayHeader();
$total = calculateTotal(10, 5);
processOrder($total);
displayFooter();