Description:
------------
When using filter_var(X, FILTER_VALIDATE_INT), where X is:
- true - result is int(1)
- false - result is bool(false)
- 1.1 - result is bool(false)
- 0.0 - result is int(0)
- '0.0' - result is bool(false)
- '-0.0' - result is bool(false)

Problems:
- Why true is reported as valid 1 but false is invalid? Both are invalid.
- Why 0.0 is reported as valid? Other floats are not.
- Why the same 0.0 as a string is reported as invalid? This is inconsistent
  with ints: filter(X = '1') === filter(X = 1), i.e. ints as strings pass as valid.

Test script:
---------------
// Prints int(1).
var_dump(filter_var(true, FILTER_VALIDATE_INT));

// ...but this prints bool(false).
var_dump(filter_var(false, FILTER_VALIDATE_INT));

// --------

// Prints bool(false).
var_dump(filter_var(1.1, FILTER_VALIDATE_INT));

// ...but this prints int(0).
var_dump(filter_var(0.0, FILTER_VALIDATE_INT));

// ...but this again is bool(false).
var_dump(filter_var('0.0', FILTER_VALIDATE_INT));

// Also bool(false).
var_dump(filter_var('-0.0', FILTER_VALIDATE_INT));


Expected result:
----------------
I expect these to return bool(false):

var_dump(filter_var(true, FILTER_VALIDATE_INT));

var_dump(filter_var(0.0, FILTER_VALIDATE_INT));