添加用户头像时无法move_uploaded_file

又回到另一个新手问题。我一直在开发一个文档，允许用户将自己的头像上传到我正在创建的博客中，以学习一些 PHP。我已经在这个文档上工作了两天，我花了六个多小时的搜索和尝试不同的东西来修复它，但我就是无法让它通过这个：

if(move_uploaded_file($_FILES['avatar']['name'], $target)){ 
    //good message
    echo "Your avatar was successfully uploaded."; 
    }else{
    //bad message
    echo "Your avatar couldnt be uploaded, please contact an admin."; 
    }

经过大约一个小时的尝试，它确实最终发送了"坏消息"，但我不太确定为什么它会给我"坏消息"，对我来说一切看起来都很好。

完整代码：

<?php
session_start();
if (isset($_SESSION['username'])){

if (isset($_POST['submit']) && isset($_FILES['avatar'])) {
        $con = mysql_connect("localhost","root","");
        if (!$con){
            die('Could not connect: ' . mysql_error());
        }
    mysql_select_db('webserver', $con);
    $username = $_SESSION['username'];
    $query = "SELECT * FROM users WHERE username = '$username'";
    $result = mysql_query($query);                   
    $row = mysql_fetch_array($result);
    $id = $row['id'];
    //Directory to save stuff
    $target = "images/useravatars"; 
    $target = $target . basename($_FILES['avatar']['tmp_name']);
    //Save the avatar
    if(move_uploaded_file($_FILES['avatar']['name'], $target)){ 
    //good message
    echo "Your avatar was successfully uploaded."; 
    }else{
    //bad message
    echo "Your avatar couldnt be uploaded, please contact an admin."; 
    }
}else{
echo "38";
}
}
?>

<form enctype="multipart/form-data" action='uploadavatar.php' method='POST'>
    <table>
        <tr>
            <td>
            Upload an avatar:
            </td>
        </tr>
            <td>
            <input type='file' name='avatar'>
            </td>
        </tr>
    </table>
    <p>
        <input enctype='multipart/form-data' type='submit' name='submit' value='Submit'>
    </p>
</form>

顺便说一句，我很抱歉那里可能有一堆无用的代码，我花了很多时间让它足够远，给我一个错误。