PHP Script fix all bugs + add many new features

The script runs in PHP and uses Apache mod rewrite and XML files. The script is a content management system. I will give full details of the script via PM, including the url of my website. I need the winning bidder to go through the script thoroughly and fix all the current bugs in code (some known bugs as well as all unknown bugs). Further, I need many new features added (30+) to the script after all the current bugs are fixed, so I can release a new version. I want several variations of the script too - a single use license and several uses/unlimited. Again, will give more details via PM. The winning bidder will have to do very thorough testing of everything and go through ALL the code - I do not want any bugs to remain or any new ones introduced. Also, you will have to remain available after you install the finished product just in case any unexpected issues come up that you will need to fix quickly (but I am hoping that this script will be 100% tested thoroughly and all the bugs eliminated).