Problem with uploading files using Wordpress

Question

I’m having a little trouble sending files. I made a functional code, on my local PC, that sent the files to my project folder using the move_uploaded_file, worked correctly. Only I want to apply this same code on my site and I can not at all. My site is developed in Wordpress. Does it have anything to do with Wordpress?

$target_dir = 'arquivos/';
if( isset($_FILES['file']['name'])) {

  $total_files = count($_FILES['file']['name']);

  for($key = 0; $key < $total_files; $key++) {

    // Check if file is selected
    if(isset($_FILES['file']['name'][$key])
                      && $_FILES['file']['size'][$key] > 0) {

      $original_filename = $_FILES['file']['name'][$key];
      $target = $target_dir . basename($original_filename);
      $tmp  = $_FILES['file']['tmp_name'][$key];
      move_uploaded_file($tmp, $target);
    }
  }
}