PHP has a component called BCMath which does arbitrary-precision, decimal arithmetic. I used BCMath in my decimal/binary converter because:

- Arbitrary-precision lets it operate on very large and very small numbers, numbers that can’t be represented in standard computer word sizes.
- Decimal arithmetic lets it use the same algorithms I’d use to convert between decimal and binary by hand.

(If you’ve written a conversion routine in standard code, especially one to convert decimal fractions to binary, you’ll see the advantage of the second point.)

This article describes the implementation of my conversion routines with BCMath.