Wordpress Upload Image from front-end and get its url

function agp_process_woofile($files, $post_id, $caption){


  require_once(ABSPATH . "wp-admin" . '/includes/image.php');
  require_once(ABSPATH . "wp-admin" . '/includes/file.php');
  require_once(ABSPATH . "wp-admin" . '/includes/media.php');

    $attachment_id = media_handle_upload($files, $post_id);

 $attachment_url = wp_get_attachment_url($attachment_id);
  add_post_meta($post_id, '_file_paths', $attachment_url);

    $attachment_data = array(
    'ID' => $attachment_id,
    'post_excerpt' => $caption
  );

  wp_update_post($attachment_data);

  return $attachment_id;

} 

REF:http://stackoverflow.com/questions/17351348/upload-image-from-front-end-and-get-its-url