翻译成PHP代码是什么?

哪位大哥帮忙翻译成PHP? JAVA不懂, 对方没有PHP SDK 谢谢了.

/**
   * 签名算法
   * 
   * @return
   * @throws Exception
   */
   public static String createSign(String param) throws Exception {
       StringBuffer result = new StringBuffer();
       MessageDigest md5 = MessageDigest.getInstance("MD5");
       md5.update(param.getBytes("UTF-8"));
       byte[] b = md5.digest();
       for(int i=0;i< b.length;++i) {
           int x = b[i]&0xFF;
           int h = x>>>4;
           int l = x&0x0F;
           result.append((char)(h+((h<10)?'0':'a'-10)));
           result.append((char)(l+((l<10)?'0':'a'-10)));
       }
       return result.toString().substring(8, 24);
   }