How can PHP developers troubleshoot incorrect VAT calculations in existing codebases?

To troubleshoot incorrect VAT calculations in existing PHP codebases, developers can start by checking the logic used for calculating VAT, ensuring that the correct tax rate is being applied to the appropriate values. They can also verify that the input values are being passed correctly and that any rounding errors are being handled properly. Additionally, using debugging tools or printing out intermediate values can help identify where the issue lies.

// Example code snippet for calculating VAT with correct tax rate
$price = 100; // Price before VAT
$vatRate = 0.20; // VAT rate (20%)

$vatAmount = $price * $vatRate;
$totalPrice = $price + $vatAmount;

echo "Price: $price\n";
echo "VAT Amount: $vatAmount\n";
echo "Total Price: $totalPrice\n";