PHP通过下载和查看文件上传到MySQL数据库

Does not download correctly: can't open the link. Help appreciated. I am new to PHP and MySQL. I have MySQL set to BLOB for the content and I am not sure how to be clearer, I can see the link(s) for the file with the respective id to the file content $id in the url, but when I click on the link nothing opens up, I want to be able to open the file inthe brownser. I intend on being able to open .zip files and extract in later development. A sfar as security please also explain in good details so I can learn. I see my code was mod, but still not working in the array link.

UPLOAD.PHP:

<?php 
$dbname="upload";
$host="localhost";
$user="SELF";
$pass="PICME";
$link = mysql_connect($hostname, $user, $pass);
mysql_select_db($dbname, $link);
?>
<form method="post" enctype="multipart/form-data">
   <table width="350" border="0" cellpadding="1" cellspacing="1" class="box">
      <tr> 
         <td width="246">
            <input type="hidden" name="MAX_FILE_SIZE" value="2000000">
            <input name="userfile" type="file" id="userfile"> 
         </td>
         <td width="80"><input name="upload" type="submit" class="box" id="upload" value=" Upload "></td>
      </tr>
   </table>
</form>
<?php
if(isset($_POST['upload']) && $_FILES['userfile']['size'] > 0)
{
$fileName = $_FILES['userfile']['name'];
$tmpName  = $_FILES['userfile']['tmp_name'];
$fileType = $_FILES['userfile']['type'];
$fileSize = $_FILES['userfile']['size'];
$fp      = fopen($tmpName, 'r');
$content = fread($fp, filesize($tmpName));
$content = addslashes($content);
fclose($fp);
if(!get_magic_quotes_gpc())
{
$fileName = addslashes($fileName);
}
$query = "INSERT INTO upload (name, type, size, content) ".
"VALUES ('$fileName', '$fileType', '$fileSize', '$content')";
mysql_query($query) or die('Error, query failed'); 
echo "<br>File $fileName uploaded<br>";
} 
?>'
(DOWNLOAD.PHP)FILE
'<?php
$dbname="upload";
$host="localhost";
$user="SELF";
$pass="PICME";
$link = mysql_connect($hostname, $user, $pass);
mysql_select_db($dbname, $link);
$query = "SELECT id, name FROM upload";
$result = mysql_query($query) or die('Error, query failed');
if(mysql_num_rows($result) == 0)
{
echo "Database is empty <br>";
} 
else
{
while(list($id, $name) = mysql_fetch_array($result))
{
?>
<a href="download.php?id=<?php echo urlencode($id);?>"><?php echo urlencode($name);?></a> <br>
<?php 
}
}
exit;
?>
<?php
$dbname="upload";
$host="localhost";
$user="SELF";
$pass="PICME";
$link = mysql_connect($hostname, $user, $pass);
mysql_select_db($dbname, $link);
$query = "SELECT id, name FROM upload";
if(isset($_GET['id'])) 
{
// if id is set then get the file with the id from database
$id    = $_GET['id'];
$query = "SELECT name, type, size, content " .
"FROM upload WHERE id = '$id'";
$result = mysql_query($query) or die('Error, query failed');
list($name, $type, $size, $content) =                     mysql_fetch_array($result);
$content = $row['content']; 
header("Content-Disposition: attachment; filename=$name");
header('Content-type: image/jpeg' . $type); // 'image/jpeg' for JPEG images
header('Content-Length:' . $size);
exit;
print $content;
ob_clean();
flush();
echo $content;
}
?>

It seems you are not validating the Mime type of the file while uploading and setting Mimetype for JPEG while downloading. Please make sure you are uploading the correct file format. Also, the id is urlencoded but not decoded while retrieving from DB.