发送到上传类的表单数据是长度字段的未定义索引

Question

我有一个表单字段，其中包含我要用于课程的所有信息，这些信息会将歌曲上传到目录并将一些数据输入到数据库中。脚本尚未完成，但目前我想测试上传功能。 PHP正在为长度输入字段抛出一个未定义的索引消息。我无法弄清楚出了什么问题！

<?php
require_once('config/config.php');

require('classes/musicClass.php');

$music = new music();

include('views/header.php'); 

if (isset($_SESSION['user_id']) && $_SESSION['user_id'] == 1) {

?>

<form action="mypage.php" method="post" enctype="multipart/form-data">
<label for="name">Track Name</label>
<input type="text" name="track_name" placeholder="Name of song" id="name" class="text    ui-widget-content ui-corner-all">
<label for="name">Artist</label>
<input type="text" name="artist" placeholder="Name of artist" id="artist" class="text ui-widget-content ui-corner-all">
<label for="genre">Genre</label>
<input type="text" name="genre" placeholder="Genre" id="genre" value="" class="text ui-widget-content ui-corner-all">
<label for="subgenre">Sub-Genre</label>
<input type="text" name="sub_genre" placeholder="Sub-Genre" id="subgenre" value="" class="text ui-widget-content ui-corner-all">
<label for="mood">Tag</label>
<input type="text" name="tag" placeholder="Tag" id="tag" value="" class="text ui-widget-content ui-corner-all">
<label for="mood">Tag2</label>
<input type="text" name="tag2" placeholder="Tag 2" id="tag" value="" class="text ui-widget-content ui-corner-all">
<label for="mood">Tag3</label>
<input type="text" name="tag3" placeholder="Tag 3" id="tag" value="" class="text ui-widget-content ui-corner-all">
<label for="length">Full langth?</label><br />
Yes: <input type="radio" name="length" value="Yes"><br />
No: <input type="radio" name="length" value="No"><br />
<label for="description">Description:</label>
<input type="textarea" name="description" placeholder="Type a description of your song" id="description" value="" class="text ui-widget-content ui-corner-all">
<label for="file">File:</label>
<input type="file" name="file" id="file"><br>
<input type="submit" name="upload_submit" value="Upload"  id="file" />

<?php
} else {
echo 'You are not allowed to use this page';
} 
?>

<?php require_once('views/footer.php'); ?>


<?php

class music {

public $file_name = '';

public $errors = array();

public $notice = array();

public $db_connect = null;

public function __construct()
{
    session_start();

        if(isset($_POST['upload_submit'])) {
            if(isset($_SESSION['user_id'])) {
                if($_SESSION['user_id'] == 1) {
                    $this->upload_music($_POST['track_name'], $_POST['artist'], $_POST['genre'], $_POST['sub_genre'], $_POST['tag'], $_POST['tag2'], $_POST['tag3'], $_POST['length'], $_POST['description']);
            } else {
                $this->notice[] = 'You are not authorized to use this feature';
            }
        } else {
            $this->notice[] = 'You must be logged in to upload';

        }
    }
}

private function database_connection()
{
    // if connection already exists
    if ($this->db_connect != null) {
        return true;
    } else {
        try {
            $this->db_connect = new PDO('mysql:host='. DB_HOST .';dbname='. DB_NAME .   ';charset=utf8', DB_USER, DB_PASS);
            return true;
        } catch (PDOException $e) {
            $this->errors[] = 'There was an error:' . $e->getMessage();
        }
    }
    // default return
    return false;
}

public function upload_music($track_name, $artist, $genre, $sub_genre, $tag, $tag2,   $tag3, $length, $description)
{
    if(empty($track_name)){
        $this->errors[] = 'Track name field is empty';
    } elseif(empty($artist)){
        $this->errors[] = 'Artist field is empty';
    } else {

        $allowed = array("wav", "mp3", "mp4", "aiff", "m4a");
        $temp = explode(".", $_FILES["file"]["name"]);
        $extension = end($temp);
            if (in_array($extension, $allowed)){
              if ($_FILES["file"]["error"] > 0)
                {
                $this->errors[] = "Return Code: " . $_FILES["file"]["error"] . "<br>";
                }
              else
                {
                if (file_exists("C:/Apache24/grant/uploads/" . $_FILES["file"]["name"]))
                  {
                  $this->errors[] =  $_FILES["file"]["name"] . " already exists. ";
                  }
                else
                  {
                      move_uploaded_file($_FILES["file"]["tmp_name"],
                  "C:/Apache24/grant/uploads/" . $_FILES["file"]    ["name"]);
                  $this->notice[] = "Stored in: " . "uploads/" .             $_FILES["file"]["name"];
                  }
                }
              }
        else
        {
            $this->errors[] = "Invalid file";
        }
    }
}
}

?>