While PHP/CURL's cookie management is extremely useful to webbot developers, it has a few shortcomings. Here are some ideas for improving on what PHP/CURL already does.
Design a script that reads cookies directly from the HTTP header and programmatically sends the correct cookies back to the server in the HTTP header of page requests. While you're at it, improve on PHP/CURL's ability to manage cookie expiration dates.
For security reasons, sometimes administrators do not allow scripts running on hosted webservers to write local files. When this is the case, PHP/CURL is not able to maintain cookie files. Resolve this problem by writing a MySQL-based cookie management system.
Write a webbot that pools cookies written by two or more ...