How to upload to a static content server with php?

I am launching a web application soon that will be serving a fair amount of images so I'd like to have a main web server and a static content server and possibly a separate database server later on.

I'd like the user to:

1. login and be able to upload a photo
2. the photo is renamed a randrom string
3. the photo is processed into a thumbnail
4. the photo and thumbnail are stored into a filesystem on the static server.
5. the photo and thumbnail's directory and filename are stored in a mysql database

The problem is I don't know how to have the user instantly upload an image to a separate server.

I thought about using amazon s3, but you can't edit filenames before posting them. (through POST, I'd rather not use the REST api)

I could also use php's ftp function to upload to a separate server, but I'd like to dynamically create folders based on the properties of the image (so I don't have all the images in one big folder obviously), but I don'开发者_开发百科t know how this would work if I used ftp...

Or I could save them locally and use a CDN, I'm not too familiar with CDN's so I don't know if using them this way would be appropriate or cost-effective.

What are my options here? I'd like the images to be available instantly (no cron jobs/queues)

Thanks.

You can create directories over FTP with PHP, so that should not be a showstopper.

I thought about using amazon s3, but you can't edit filenames before posting them. (through POST, I'd rather not use the REST api)

If you let your PHP server do the uploading to S3 via POST, you can name the files whatever you want. You should do that anyway, letting your users upload to S3 directly, without your PHP code inbetween, sounds like bad for security to me.