Description:
------------
When you cast a string variable to boolean type there are some cases in which the cast doesn't work properly, i think.

Reproduce code:
---------------
$arrTestVars = array(
  '0',
  '-0',
  '+0',
  '0.0',
  '0e0',
  '0.0e0'
);

foreach($arrTestVars as $strTestVar) {
  var_dump(
    (bool)$strTestVar
  );
}


Expected result:
----------------
// Expected Result => (bool)false, (bool)false, (bool)false, (bool)false, (bool)false, (bool)false

All the tests above should be evaluated to false, because
(bool)0.0 === false
(bool)0e0 === false
and so on.

Now one has to use the workaround (bool)(int)'0.0' === false ...


Actual result:
--------------
// Actual Result => (bool)false, (bool)true, (bool)true, (bool)true, (bool)true, (bool)true