} else if (subject instanceof StringValue) {
} else if (subject.isset()) {
  public static Value preg_replace(Env env,                                   Value pattern,                                   Value replacement,                                   Value subject,                                   @Optional("-1") long limit,                                   @Optional @Reference Value count)  {    if (subject instanceof ArrayValue) {      ArrayValue result = new ArrayValueImpl();      for (Value value : ((ArrayValue) subject).values()) {        result.put(pregReplace(env,                               pattern,                               replacement,                               value.toStringValue(),                               limit,                               count));      }      return result;    } else if (subject instanceof StringValue) {      return pregReplace(env, pattern, replacement, subject.toStringValue(),			 limit, count);    } else      return NullValue.NULL;  }