Working with Money in PHP: The Value Object Approach

Why Money Handling is Different Financial software isn't like building a blog or todo app. When users click «Pay $99.99» they expect exactly $99.99 to leave their account - not $99.989999999 or $100.000000001. A rounding error of 0.01 cents might seem trivial. But multiply that across: 10,000 daily transactions Monthly payroll for 500 employees Years of accumulated accounting discrepancies Suddenly your «tiny float imprecision» becomes thousands of dollars in lost revenue, failed audits, or angry customers. The Silent Killer: Float Precision 90% of PHP projects handle money wrong. Here's the classic trap: $subtotal = 0.1 + 0.2; // Should be 0.3 $tax = $subtotal * 1.08; // Should be 0.324 $total = $tax + 0.50; // Should be 0.824 echo json_encode([ 'subtotal' => $subtotal, // 0.30000000000000004 😱 'tax' => $tax, // 0.32400000000000006 'total' => $total // 0.8240000000000001 ]); Your API returns garbage numbers. Your accountant calls in a panic. Customers complain about wrong ch