Uploaded medium blob truncated on download - php

Question

I upload a blob to my sql database table with a field that is defined to be of size medium blob. The blob is actually a pdf file of size 4.3mb. The file is uploaded via ftp. After upload, some php code inserts it into the database. I've checked the file within the ftp folder and I can view it correctly. I've checked the file (blob) within the database and I can view it correctly. Both sizes show 4.3mb. If I try to download the file using some code provided by another programmer (below), the file is truncated at about 300kb.
if (!($dbLink = mysql_pconnect($db_server,$db_id,$db_pwd)))
{
print("Failed to connect to database!<BR>\n");
exit();
}
if(!mysql_select_db($db_name,$dbLink))
{
print("Cannot use the database!<BR>\n");
exit();
}
$query = "SELECT name, type, content FROM table_name WHERE link_id = '" . $id . "'";
$result = mysql_query($query, $dbLink) or die('Error, query failed');
list($name, $type, $content) = mysql_fetch_array($result);
//header("Content-length: $size");
header("Content-type: $type");
header("Content-Disposition: attachment; filename=$name");
echo $content;
exit;
I checked my maximum packet size within MySQL and it appears to be about 256mb. My php.ini shows 10mb for posts. I'm at a loss as to why the file is truncated. Can someone please point me in the right direction to solve this?

Answer 1

The PDO interface between PHP and MySQL offers a streaming scheme for LOB-handling. Seeing as how the mysql_ interface was abandoned years ago by its developers, it might be worth trying this.
See this: http://www.php.net/manual/en/pdo.lobs.php
You might consider using code like this.
$db = new PDO('mysql:dbname=testdb;host=127.0.0.1', 'username', 'password');
$query = "SELECT name,
type,
OCTET_LENGTH(content) AS length,
content
FROM table_name
WHERE link_id = :link_id
LIMIT 1";
$stmt = $db->prepare($query);
$stmt->execute(array(":link_id" => $id));
$stmt->bindColumn(1, $name);
$stmt->bindColumn(2, $type);
$stmt->bindColumn(3, $length);
$stmt->bindColumn(4, $data, PDO::PARAM_LOB); /* binds as a stream */
if ($stmt->fetch(PDO::FETCH_BOUND)) {
header("Content-Type: $type");
header("Content-Length: $length");
header("Content-Disposition: attachment; filename=$name");
fpassthru($data);
}
Sorry to say I haven't debugged this. But it's a fairly common use case.

Answer 2

I have resolved this with a different methodology. No matter what I tried from several different examples, I could not get the suggested PHP code to stop truncating files. I stopped storing the file as an attachment in the database, and, simply stored it in a separate folder on the server. The database was updated to insert a "path" link for the file. I changed the php code to:
// Construct an HTTP header that will force the browser to display/download the file.
header("Location: ".$location);
ob_flush();
exit;
This forced a relocation to the actual file stored on the server. The file now opens in the browser. Note: I also had to change some html code to force the file to open in a new tab in the browser.