RobThree\Auth\TwoFactorAuth::getCode PHP Method

    public function getCode($secret, $time = null)
    {
        $secretkey = $this->base32Decode($secret);
        $timestamp = "" . pack('N*', $this->getTimeSlice($this->getTime($time)));
        // Pack time into binary string
        $hashhmac = hash_hmac($this->algorithm, $timestamp, $secretkey, true);
        // Hash it with users secret key
        $hashpart = substr($hashhmac, ord(substr($hashhmac, -1)) & 0xf, 4);
        // Use last nibble of result as index/offset and grab 4 bytes of the result
        $value = unpack('N', $hashpart);
        // Unpack binary value
        $value = $value[1] & 0x7fffffff;
        // Drop MSB, keep only 31 bits
        return str_pad($value % pow(10, $this->digits), $this->digits, '0', STR_PAD_LEFT);
    }

 public function testKnownTestVectors_sha512()
 {
     //Known test vectors for SHA512: https://tools.ietf.org/html/rfc6238#page-15
     $secret = 'GEZDGNBVGY3TQOJQGEZDGNBVGY3TQOJQGEZDGNBVGY3TQOJQGEZDGNBVGY3TQOJQGEZDGNBVGY3TQOJQGEZDGNBVGY3TQOJQGEZDGNA';
     //== base32encode('1234567890123456789012345678901234567890123456789012345678901234')
     $tfa = new TwoFactorAuth('Test', 8, 30, 'sha512');
     $this->assertEquals('90693936', $tfa->getCode($secret, 59));
     $this->assertEquals('25091201', $tfa->getCode($secret, 1111111109));
     $this->assertEquals('99943326', $tfa->getCode($secret, 1111111111));
     $this->assertEquals('93441116', $tfa->getCode($secret, 1234567890));
     $this->assertEquals('38618901', $tfa->getCode($secret, 2000000000));
     $this->assertEquals('47863826', $tfa->getCode($secret, 20000000000));
 }