How can PHP variables be used to optimize code readability and functionality?

Using PHP variables can optimize code readability and functionality by allowing you to store values that are reused multiple times in your code, making it easier to update them in one place. Additionally, variables can make your code more self-explanatory by giving meaningful names to values or calculations. This can help other developers understand your code more easily and make maintenance tasks simpler.

// Example of using variables to optimize code readability and functionality
$base_price = 100;
$tax_rate = 0.15;
$discount = 0.10;

$total_price = $base_price + ($base_price * $tax_rate) - ($base_price * $discount);

echo "Total price after tax and discount: $" . $total_price;