/**
* Converts the inserted string boolean to a PHP boolean.
*
* @param string $bool
*
* @return null|bool
*/
protected function convertStringToBool($bool)
{
$bool = strtoupper($bool);
if ($bool === strtoupper($this->schema->false())) {
return false;
} elseif ($bool === strtoupper($this->schema->true())) {
return true;
} else {
return;
}
}