PDO not inserting more than one row in table - php

Question

I'm having trouble inserting image data into my database. I have a table called images. When dumped with PHPMyAdmin it looks like this:
CREATE TABLE IF NOT EXISTS `images` (
`id` int(11) NOT NULL,
`orig_name` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`hash` varchar(6) COLLATE utf8_unicode_ci NOT NULL,
`filename` varchar(12) COLLATE utf8_unicode_ci NOT NULL,
`uploaded` datetime NOT NULL,
`views` int(11) NOT NULL DEFAULT '0',
`album_id` int(11) DEFAULT NULL,
`user_id` int(11) DEFAULT NULL,
`server_id` int(11) NOT NULL,
PRIMARY KEY (`id`),
KEY `user_id` (`user_id`),
KEY `server_id` (`server_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
This is the code I'm using to insert rows:
// Database connection
$db = new PDO('mysql:host=localhost;dbname=testdb', 'root', '');
// some code...
$st = $db->prepare('INSERT INTO `images` (orig_name, hash, filename, uploaded, server_id)
VALUES (?, ?, ?, ?, (SELECT `id` FROM `servers` WHERE `name` = ?))');
$st->execute(array($origName, $fileHash, $filename, date('c'), $server));
// more code...
// Database cleanup
$st = null;
$db = null;
The script returns no errors, and works flawlessly for the first row inserted. If the script runs again, it fails to insert any more rows in the images table. I see no reason why it'd behave like this, the data going into each field is unique each time (except for the server_id field).

Answer 1

Your id field isn't set to auto_increment.
The first record that you post will be added, with a NULL as id; the second record won't be added because there's already a record with NULL as the primary key, so it'll fail - you don't have any error checking in the code, so it won't be printing out the errors it's getting back.