Upload images from my server to password protected site

I'm in the process of building a site that will help to organize my business. But I'm at a roadblock. Our site is coded in PHP and MySQL and as it currently stands, our contractors can upload images to our site, our site relabels the pictures and associates them with a work order (for ability to search later, if needed), then stores the images in our database.

However, what I want to do is have the images uploaded to their respective work order o开发者_如何学编程n our supplier's site. I have contacted our supplier and they will not allow us to access their server directly through the POST commands. So I'm curious if there is a way to still have our images uploaded from our site to our supplier's site. Their site is password protected. On their site, I find the work order associated to the work order and manually upload the images, but I'd like to find a way to do this automatically. The work order numbers between their site and ours are the same. Any ideas?

New Info

The comment I left below just states that I have to actually manually click the upload button, choose which photos to upload, then click "upload" to have the images uploaded. FTP is not allowed either.

If by "manually" you mean all by www after logging in, you can use CURL to simulate login session to their website (access login page to obtain session cookie, then post login data with that session cookie, and then with authorized session cookie you can GET/POST whatever you want from their website as authorized user). Use Firebug to track what requests are made and what data are passed from/to their website.

Since using CURL can be painfull (it's syntax is far from user friendly) you can try grab and extract Zend_Http from Zend Framework so you will have very easy syntax and it even work without CURL if you haven't it on your servers.

if they will grant you ftp access you can programatically transfer the images to them that way or if they have some sort of api exposing methods to upload images

By "manually upload", you mean via FTP? You can do it with PHP. Here is the documentation.

For security reasons, I suggest you create an FTP user on your client's server which only has access to the images directory, and connect trough that account.