将C＃sha256哈希转换为等效的PHP

Question

I need to convert some C# code into a PHP equivalent to work with a SOAP web API. All of their examples are in C#. I think I have the equivalent PHP function, but my SOAP requests are returning either 'Bad Request' or 'Unauthorized - Invalid API Key' - while the example page on the API page works with my keys and the request URLs look the same sans the digest message being passed. The API and client ID are definitely correct.

Here is the C# code:

private string GenerateDigest(long currentTime)
    {
        SHA256Managed hashString = new SHA256Managed();
        StringBuilder hex = new StringBuilder();
        byte[] hashValue = hashString.ComputeHash(Encoding.UTF8.GetBytes(String.Format("{0}{1}", currentTime, txtApiKey.Text)));

        foreach (byte x in hashValue)
        {
            hex.AppendFormat("{0:x2}", x);
        }

        return hex.ToString();
    }

Here is the PHP function I wrote to try to do what C# is doing:

public static function generateDigest($api_key) {
  return hash('sha256', time() . mb_convert_encoding($api_key, 'UTF-8'));
}

I am not very fluent in C# so I assume where I am going wrong is where it is doing hex.AppendFormat(). I am not sure what this is supposed to be in PHP. The end result is a hash that is appended to a URL to generate a SOAP request, like this:

https://payments.homeaway.com/tokens?time=1387385872013&digest=1bd70217d02ecc1398a1c90b2be733ff686b13489d9d5b1229461c8aab6e6844&clientId=[redacted]

Edit:

Here is the currentTime variable being passed in C#.

// Request validation setup
TimeSpan timeSinceEpoch = DateTime.UtcNow - new DateTime(1970, 1, 1);
long currentTime = (long)timeSinceEpoch.TotalMilliseconds;
string digest = GenerateDigest(currentTime);

Answer 1

I've the same problem coverting this to php code here's my code to solve the problem :

 function generateDigest($time, $api_key) {
    $hash = hash('sha256', $time . mb_convert_encoding($api_key, 'UTF-8'), true);
    return $this->hexToStr($hash);
}

function hexToStr($string){
    //return bin2hex($string);
    $hex="";
    for ($i=0; $i < strlen($string); $i++)
    {
        if (ord($string[$i])<16)
            $hex .= "0";
        $hex .= dechex(ord($string[$i]));
    }
    return ($hex);
}

Answer 2

If anyone is looking for this the answer has to do with time. PHP's time() function returns time in seconds where the call in C# returns milliseconds.

Therefore, the correct way to get $currentTime is

$currentTime = time() * 1000;

This has been tested with the API.