PHP - upload audio file to Dropbox and calculate audio length

Hi, I need a fairly simple PHP/Jquery script written which will allow audio and PDF files to be chosen from the user's computer and uploaded to Dropbox via the Dropbox API (I can supply API credentials).

Ideally a multi-file chooser which shows upload progress of each file and allows for chunking of large files as some might be 200MB+.

After/during upload, the script needs to calculate the length of each audio file (hours, minutes, seconds) and output the filename, a unique link/path to the file on Dropbox and the audio length (obviously this will be 0 for a pdf), so these can be saved to a database. The database is already in place so no work is required on that, just the file upload and presentation of the results.

I don't mind if it uses 3rd party classes or packages as long as they are safe and secure, but NO development framework as the finished code will need to be changed easily in the future and integrate easily into an existing system.

Budget is not fixed and I will pay a fair price for the best solution.

Please note, generic responses will not be considered so please only respond if you have read and understand the brief, and can suggest a suitable solution.

Please let me know if you have any queries. Thanks.