mkdir无法正常工作

Question

The mkdir() is not working for me. What is going wrong in this code?

  foreach($_FILES['documents']['tmp_name'] as $key => $tmp_name)
 {
   $file_name = $key.$_FILES['documents']['name'][$key];
   $file_size =$_FILES['documents']['size'][$key];
   $file_tmp =$_FILES['documents']['tmp_name'][$key];
   $file_type=$_FILES['documents']['type'][$key];
   $name = $_POST['uname'][$key];
   $email = $_POST['uemail'][$key];
   $password = $_POST['epass'][$key];
   $file_names = time().$file_name;

   $query = "INSERT INTO `table` VALUES
  ('', '$name', '', '', '$email', '$password', 1, '', 1, '', '$file_names',   '$file_names', '', '', '', '', 1, '', '', '1', '')";

   $resultl =  $db->insert($query);

   $userId = mysql_insert_id();

   $output_dir = $_SERVER['DOCUMENT_ROOT']."uploads/users/$userId/";
   mkdir($output_dir, 0777);
   chmod($output_dir, 0777);

The directory is not being created. I searched in Stack Overflow for the solution and applied some of them but still no success. I am using wamp; when I move the uploaded image without creating directory, then it moves the file.

Answer 1

$output_dir = $_SERVER['DOCUMENT_ROOT'] . "/uploads/users/$userId/";

mkdir($output_dir, 0777, true);