function addOddDigits($n, $second_n) {
$multiply = 1;
$odd = 0;
while ($n != 0) {
if ($n % 2 != 0) {
$odd += ($n % 10) * $multiply;
$multiply *= 10;
}
$n = intval($n / 10);
}
return $second_n * $multiply + $odd;
}
$n = 12734;
$second_n = 100;
echo addOddDigits($n, $second_n);
/*
run:
100173
*/