/**
* _mapbin
*
* Used with array_map to map the characters from a base32
* character set directly into a binary string
*
* @param string $chr The character to map
*
* @return string String of 0's and 1's
*
* @access private
*/
private function _mapbin($chr)
{
return sprintf('%08b', strpos(self::CSRFC3548, $chr));
}