If you are getting paid for this project, be prepared to give a fair percentage of that amount for the percentage of the mysql work you are contracting out.
If you are not getting paid for this project, you have a more serious problem. Getting someone to spend the time to plan, design, write, test, debug, and integrate their work with the portion you are going to be doing is going to be difficult without some worthwhile benefit to them.
Even if this work in minimal, you are talking about at least one hour of time to bring someone up to speed on the project (do you have a written specification and a written scope of work?). The few minutes or few 10's of minutes that you see someone taking to respond to a mysql question in a Forum like this is just the minimal basics. To get real world, bullet-proof, tested, debugged code takes at least 5 times as long as a simple reply in a Forum.
If you are learning PHP, developing PHP code, or debugging PHP code, do yourself a favor and check your web server log for errors and/or turn on full PHP error reporting in php.ini or in a .htaccess file to get PHP to help you.