PHP - Check for distinct filename on file upload - php

Question

I'm pretty new to PHP. I hate to have to ask questions, because I'm sure this is documented somewhere, but after looking for a while, I just cannot seem to put two and two together.
I have a program that will allow multiple images to be uploaded to an item within the database. Basically, for each item in the database, there might be multiple image uploads.
Example:
Item: Xbox 360
Images:
Xbox360.jpg
side.jpg
front.jpg
The image and item information is all stored in the database (MySQL), but the images are stored within the filesystem, and the database points to the URL of the image(s) in the filesystem.
The problem I'm having is that everything works as expected, except it allows duplicate image names to be written to the database. It doesn't allow duplicate images to be written to the filesystem, which I'm happy with. I want to make sure that the name of an image is only added once to the database. If the image name is a duplicate to another, it needs to not write to the database.
add_db.php:
$uniqueDir = uniqid();
$directory = "img/$uniqueDir/";
db_addItem($id_category, $name, $cost, $description, $qty, $directory); //Adds to the `items` table
foreach ($_FILES['i_file']['name'] as $filename) {
if ($filename != '' && $filename != 'No file chosen') {
//I think above is where I check for unique image names
$url = "img/$uniqueDir/$filename";
db_addImg($url, $filename); //Adds to the `img` table
$item_picsID = get_item_PicsID($filename, $url);
$itemID = get_itemID($directory);
db_insertImg($itemID, $item_picsID);
}
}
addFilesystem($directory); //Writes image(s) to filesystem
function db_addImg($url, $filename) {
include 'mysql_login_pdo.php';
// Create the SQL query
$query = "INSERT INTO img (`name`, `url`) VALUES(:filename, :url)";
$stmt = $db->prepare($query);
$stmt->execute(array(
':filename' => $filename,
':url' => $url
));
}
function db_insertImg($itemID, $item_picsID) {
include 'mysql_login_pdo.php';
// Create the SQL query
$query = "INSERT INTO `item_pics` (`item_id`, `img_id`) VALUES(:itemID, :item_picsID)";
$stmt = $db->prepare($query);
$stmt->execute(array(
':itemID' => $itemID,
':item_picsID' => $item_picsID
));
$db = null;
return;
}
Everything works, except it will write duplicate image names to the database. I want the image names to be distinct. I also don't want to rename the images (if possible).

Answer 1

You can define an UNIQUE index on the name column in img table, and then use slightly modified INSERT statement in your db_addImg function:
function db_addImg($url, $filename) {
//...
$query = "INSERT INGORE INTO img (`name`, `url`) VALUES(:filename, :url)";
//...
}
It will quietly cancel any insert where the is a UNIQUE key collision, which will end up in distinct filenames across your img table.

Answer 2

I would use a filename based on the primary key from the img table as you're guaranteed it's unique.
Otherwise, you'll need to guess a unique filename with some type of hashing and then check the file system. All of which can be expensive operations.
Looks like you are using PDO, so the static method lastInsertId will get the last insert id (primary key).
For example:
// after your insert to img
$filename = 'img' . $db->lastInsertId() . $extension;
This will require changing the img table slightly. But you're better off storing meta data (file type, size, etc) in this table as opposed to the file location (as that can change).

Answer 3

I think better to use hash value of your url as the primary key. Be cause string searching is much slower as int.