How to deal with strange rounding of floats in PHP

Question

As we all know, floating point arithmetic is not always completely accurate, but how do you deal with its inconsistencies?

As an example, in PHP 5.2.9: _{(this doesn't happen in 5.3)}

echo round(14.99225, 4);  // 14.9923 
echo round(15.99225, 4);  // 15.9923 
echo round(16.99225, 4);  // 16.9922 ??
echo round(17.99225, 4);  // 17.9922 ??
echo round(25.99225, 4);  // 25.9922 ??
echo round(26.99225, 4);  // 26.9923

How would you work around this?

Answer 1

Welcome to IEEE754, enjoy your stay.

Use bc or gmp instead.