I’m a great fan of the PDO database access library in PHP 5 and use it for all of my database work in PHP. I love its’ clean, object oriented syntax and great support for prepared statements. I also like the fact that it supports most of the most common database engines.
In PDO one does not worry about sanitization and with prepared query we do have a performance boost.
The PDO does not work the same way with the Blob field type as it has a layer which inspects and sanitizes data.
PDO handles binary through LOB Large Objects. Large typically means “around 4kb or more”, although some databases can happily handle up to 32kb before data becomes “large”. Large objects can be either textual or binary in nature. PDO allows you to work with this large data type by using the PDO::PARAM_LOB type code in your PDOStatement::bindParam() orPDOStatement::bindColumn() calls. PDO::PARAM_LOB tells PDO to map the data as a stream, so that you can manipulate it using the PHP Streams API.
Display image from database
Code:
<?php
$db = new PDO('odbc:SAMPLE', 'db2inst1', 'ibmdb2');
$stmt = $db->prepare("select contenttype, imagedata from images where id=?");
$stmt->execute(array($_GET['id']));
$stmt->bindColumn(1, $type, PDO::PARAM_STR, 256);
$stmt->bindColumn(2, $lob, PDO::PARAM_LOB);
$stmt->fetch(PDO::FETCH_BOUND);
header("Content-Type: $type");
fpassthru($lob);
?>
Save Image in Database
Code:
<?php
$db = new PDO('odbc:SAMPLE', 'db2inst1', 'ibmdb2');
$stmt = $db->prepare("insert into images (id, contenttype, imagedata) values (?, ?, ?)");
$id = get_new_id(); // some function to allocate a new ID
// assume that we are running as part of a file upload form
// You can find more information in the PHP documentation
$fp = fopen($_FILES['file']['tmp_name'], 'rb');
$stmt->bindParam(1, $id);
$stmt->bindParam(2, $_FILES['file']['type']);
$stmt->bindParam(3, $fp, PDO::PARAM_LOB);
$db->beginTransaction();
$stmt->execute();
$db->commit();
?>
You may run into wall despite following all this. The cause of the same is mysql does not allow by default a file size greater than 1 MB. I was trying to upload a file size greater than one MB. After breaking my head for almost a week, I was finally able to figure out the problem source is mysql not php.
Increase the max_allowed_packet
either by adding the following line (where 16M is data packet size)
max_allowed_packet = 16M
in [mysqld] section of your my.cnf/my.ini file, or by using the following command line:
> mysqld --max_allowed_packet=16M
Maanas Royy 
How should a shared host increase max_allowed_packet for one customer without affecting other customers?
I m afraid the changes for mysql is global. You can increase the packet size for all customer and limit the packet size though php and throw error on large packet size.
If you really want to do at mysql level then you must fire a query to increase the packet size in mysql and then save your content and then again reset back the max packet size.
$db = new mysqli( ‘localhost’, ‘user’, ‘pass’, ‘dbname’ );
// to get the max_allowed_packet
$maxp = $db->query( ‘SELECT @@global.max_allowed_packet’ )->fetch_array();
echo $maxp[ 0 ];
// to set the max_allowed_packet to 500MB
$db->query( ‘SET @@global.max_allowed_packet = ‘ . 500 * 1024 * 1024 );
You can choose what approach suits you.