note 108218 deleted from filter.filters.validate by cmb

Note Submitter: Tom ---- Be aware! In contrary to what the docs say (at least in PHP 5.3.1), this line: $value = filter_var(FALSE, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE); Will return NULL - not false. In other words: a boolean FALSE is not considered a valid boolean value by this function. Also: $value = filter_var("", FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE); Will also return NULL - no matter what the docs say. So (string) FALSE is not considered a valid boolean input either. Thus be aware the that correct usage/workaround for this filter is: if (!is_bool($value)) { $value= filter_var($value, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE); } For those of you who feel this is counterintuitive, note that there is an issue filed for this in the bug-tracker. So you might want to follow the discussion there or vote for issue #49510.