protected function checkIsNull($input) {
		$isNull = $this->isNull;
		if($isNull)
			return $isNull($input);
		else
			return $input === null || $input === '';
	}
protected function checkIsNull($input) {
		$isNull = $this->isNull;
		if($isNull)
			return $isNull($input);
		else
			return $input === null || $input === '';
	}
protected function checkIsNull ( $ input ) { $ isNull = $ this -> isNull ; if ( $ isNull ) return $ isNull ( $ input ) ; else return $ input === null || $ input === '' ; }
Check if the input is null.
@param  mixed $input
@return boolean        true if the input is considered null, false otherwise.
Check if the input is null .