Why Are PHP Floating-Point Numbers Inaccurate, and How Can I Fix It?

PHP Floating Number Precision: Demystifying the Unexpected

In PHP, floating-point numbers can yield unexpected results due to the inherent nature of binary arithmetic. Unlike real numbers, binary floats are represented with limited precision, leading to approximations and potential inaccuracies.

Consider the example:

$a = '35';
$b = '-34.99';
echo ($a + $b);

This outputs 0.009999999999998 instead of the expected 0.01. This is because 34.99 and 0.01 cannot be precisely represented in binary, resulting in an approximate representation.

To overcome this issue, consider the following alternatives:

• Rounding the Result: Use round($result, 2) to round the result to two decimal places.
• Using Integers: For currency calculations, store values as integers. For instance, represent $35.00 as 3500 and $34.99 as 3499, and divide the result by 100 after calculation.

It's worth noting that PHP lacks a dedicated decimal data type found in other languages, which could potentially improve accuracy in specific scenarios. However, by understanding the limitations of floating-point arithmetic, developers can mitigate unexpected results and ensure accurate calculations.

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