protected static function _num2dec($num)
{
$n = count($num) << 1;
$b = array();
for ($i = 0; $i < $n; $i++) {
$tmp = BigInt::div($num, array(10000), 1);
$b[$i] = BigInt::zerofill($tmp[0], 4);
$num = BigInt::div($num, array(10000));
}
while (count($b) > 1 && !(int) $b[count($b) - 1]) {
array_pop($b);
}
$n = count($b) - 1;
$b[$n] = (int) $b[$n];
$b = join('', array_reverse($b));
return $b;
}