Make a php application to interact with a javascript web site and download/upload

we have already a web application built with php, using drupal, laravel framework.
our web site provides a file service where the fles supplied to customers are enctypted. in order for us to decrypt and encrypt the file we provide we must interact with a suppliers web site automatically to do it. however since a new implementation of javascripst post and response used on the vendor's web app, our current 'scraper' is unable to deal with the new set up.

i am looking for someone who can write an add in to our current application to interact with our suppliers web site to upload, decoce, and encode the files in which we suppl. alternatively i would like a totally separate application which can do the same task but then api to our application's request of a file encode/decode process.