A catastrophic bug caused by PHP accuracy calculation

When it comes to maintaining an older financial project, we find that the calculation of precision is simple and rough, first look at the code snippet:

if ($accountInfo [' Account_money '] < $repayMoney) {                rollback ();                return false;}

As shown in the code fragment variable above, the above code mainly compares account balances and repayments, both double-precision floating-point numbers, slightly modified code, so that we can see some of the output is more intuitive

if ($accountInfo [' Account_money '] < $repayMoney) {                echo "{$accountInfo [' Account_money ']}\n\r";                echo "{$repayMoney}\n\r";                Rollback ();                return false;}

Run as above code get as result

Two numbers are 1333.35, if according to the above logic, should not enter the if body, but the result is the opposite, the if body and echo out of two values, by consulting the relevant API found that the accuracy of the PHP operation, the direct +,-, *,/,<,> and other operations lost precision , so the result is not as you would like, here you are, in PHP for precision operations, you should call the relevant API, such as BC Math.

A catastrophic bug caused by PHP accuracy calculation