totp.php

<?
class OneTimePasswordGenerator {
    static $PASS_CODE_LENGTH = 6;
    static $PIN_MODULO;
    public function __construct() {
        self::$PIN_MODULO = pow(10, self::$PASS_CODE_LENGTH);
    }
     
    public function getCode($base64Secret, $time = null) {
        if (!$time) {
            $time = floor(time() / 30);
        }
        $secret = base64_decode($base64Secret);
         
        $time = pack("N", $time);
        $time = str_pad($time,8, chr(0), STR_PAD_LEFT);
         
        $hash = hash_hmac('sha1',$time,$secret,true);
        $offset = ord(substr($hash,-1));
        $offset = $offset & 0xF;
         
        $truncatedHash = self::hashToInt($hash, $offset) & 0x7FFFFFFF;
        $pinValue = str_pad($truncatedHash % self::$PIN_MODULO,6,"0",STR_PAD_LEFT);
        return $pinValue;
    }
     
    protected  function hashToInt($bytes, $start) {
        $input = substr($bytes, $start, strlen($bytes) - $start);
        $val2 = unpack("N",substr($input,0,4));
        return $val2[1];
    }
}
 
$pass_gen = new OneTimePasswordGenerator;
 
$oneTimePassword = $pass_gen->getCode('base64EncodedSecret');
 
print $oneTimePassword;
?>