In PHP 4.0.6 and earlier pow() always returned
a float, and did not issue warnings.
The base to use
raised to the power of exp
If the result can be represented as integer it will be returned as type
integer, else it will be returned as type float.
If the power cannot be computed FALSE will be returned instead.
The function will now return integer results if possible,
before this it always returned a float result. For older
versions, you may receive a bogus result for complex numbers.
PHP stops to emit a warning if the value can't be computed,
it will now silently return FALSE only.