Well, exactly. It doesn't say what happens, so pass floats or expect the unexpected. I get your point but I don't think I have ever seen documentation anywhere that covers all of the possible 'abuse' scenarios.
It is possible to add a catch-all clause to the documentation. For example any non-float argument is converted to float via floatval(), or raises an error, and so on. This behavior can be made consistent across every API so that the documentation has only one place to describe it. PHP is missing this either AFAIK.
I agree this would be ideal. Will definitely keep this in mind when writing documentation (and code) for my own tiny open source projects. All the double and triple checking just adds so much bloat most of the time...
