Hi
I have a lot of experience in debugging PHP scripts. I presume that you are referring to your installation of PHPMyAdmin, in which case I can tell you I have worked with this piece of software for over 4 years, and have been dealing with PHP and MySQL for over 6 years.
For this type of work I would charge $45 per hour, but would not expect it to take to long to find the bug, but would obviously need further details before i can give a better estimate of the time likely to be required.