In the provided PHP code, what best practices could be implemented to improve efficiency and readability?

One best practice to improve efficiency and readability in the provided PHP code is to use meaningful variable names that accurately describe their purpose. Additionally, utilizing proper indentation and spacing can make the code easier to read and understand. Lastly, breaking down complex logic into smaller, more manageable functions can improve maintainability and reusability.

// Improved PHP code with meaningful variable names, proper formatting, and modularized functions

function calculateTotalPrice($quantity, $price) {
    return $quantity * $price;
}

$quantity = 10;
$price = 5.99;

$totalPrice = calculateTotalPrice($quantity, $price);

echo "Total price for $quantity items is: $" . number_format($totalPrice, 2);