I have a big CRM system on PHP, which active works with users files, and stores them in the folder in the root of the project. Now i need to change system to save files on Amazon S3, but because of bad arhitecture of the system (it's an old open-source system) i cannot just rewrite the code. So, i got a little bit crazy idea, to intercept all system calls to one folder ("/var/www/%my_project%/uploads"), and process them in special way. PHP should be sure that it works with usual folder, file_put_contents and file_get_contents should work as usual, but in fact they should work with code which will serve files from S3 for them. Is that possible (how?), or it's too crazy idea?

Thanks :)