C# Rfc2898DeriveBytes to PHP -

i'm trying adapt following function c# php , can't work. i've searched other threads, couldn't find right answer solve problem.

public static string decrypt(string encryptedtext) {     byte[] bytes = encoding.ascii.getbytes("hello");     byte[] buffer = convert.frombase64string(encryptedtext);     byte[] rgbkey = new rfc2898derivebytes("world", bytes).getbytes(0x20);      icryptotransform transform = new rijndaelmanaged { mode = ciphermode.cbc }.createdecryptor(rgbkey, bytes);     memorystream stream = new memorystream(buffer);     cryptostream stream2 = new cryptostream(stream, transform, cryptostreammode.read);     byte[] buffer4 = new byte[buffer.length];      int count = stream2.read(buffer4, 0, buffer4.length);     stream.close();     stream2.close();      return encoding.utf8.getstring(buffer4, 0, count); } 

any appreciated. thanks!

my php code far:

<?php $key = hash_pbkdf2('sha1', 'world', 'hello', 1000, 32); $decrypted = mcrypt_decrypt(             mcrypt_rijndael_128,             $key,             'very long encrypted string',             mcrypt_mode_cbc,             'world'); ?>