PHP implementation of JAVA's StandardStringDigester

I am trying to implement Java's StandardStringDigester digest function in PHP to digest a string with the SHA-1 algorithm. I do not have experience with encryption, so I have tried a few things without understanding them. The Working Java example is following:

import java.net.URLEncoder;
import org.jasypt.digest.StandardStringDigester;
import java.io.UnsupportedEncodingException;

public class Main
{

  public static void main (String[]args)
  {
    String x = "XUXoV2VYc7zYJ8UN";
    int n = 854;
    StandardStringDigester clientsd = new StandardStringDigester ();
      clientsd.setIterations (n - 1);
      clientsd.setAlgorithm ("SHA-1");
      clientsd.setSaltSizeBytes (0);	//no salt
    String clientDigest = clientsd.digest (x);
    String URLclientDigest = "a";
    try {
         URLclientDigest = URLEncoder.encode (clientDigest, "UTF-8");
    } catch(UnsupportedEncodingException ex){
							System.out.println("Encoding not supported");
							ex.printStackTrace();
			}
      System.out.println (URLclientDigest);
  }
}

In PHP I tried few things:

$n = 854;
$x = 'XUXoV2VYc7zYJ8UN';

return hash_pbkdf2('sha1', $x, null, $n);

I also tried the above code with $n -1.
In above examples x is the message and n is the iterations.
I am not really sure what I am doing here. Perhaps there is a PHP library someone can point me to or any direcction will be appreciated.

According to the documentation of StandardStringDigester (which is part of the Jasypt library), the hash is generated as follows:

> The steps taken for creating digests are:
>
> 1. The String message is converted to a byte array
> 2. A salt of the specified size is generated (see SaltGenerator).
> 3. The salt bytes are added to the message.
> 4. The hash function is applied to the salt and message altogether, and then to the results of the function itself, as many times as
> specified (iterations).
> 5. If specified by the salt generator (see SaltGenerator.includePlainSaltInEncryptionResults()), the undigested
> salt and the final result of the hash function are concatenated and
> returned as a result.
> 6. The result of the concatenation is encoded in BASE64 or HEXADECIMAL and returned as an ASCII String.

Since no salt is used in your case, a possible PHP implementation is:

$n = 854;
$x = 'XUXoV2VYc7zYJ8UN';

$hash = $x;
for ($counter = 0; $counter < $n - 1; $counter++){
	$hash = hash('sha1', $hash, true);
}

print(base64_encode($hash)); // QGFgek+pfZ6nMk8Jn3stOe5KeEY=

with the result QGFgek+pfZ6nMk8Jn3stOe5KeEY= analogous to the Java code (before the URL encoding).

Note: If a salt is used in the Java code (e.g. with ByteArrayFixedSaltGenerator), the salt in the PHP code must be concatenated with the message before the loop: $hash = $salt . $x; (instead of $hash = $x;).