Database help needed on integrationg

Well actually I want to integrate FA as an accounting module to my software which about hotel management. So the thing is if a guest check's out and at the end of the day, when I post sales or roll over the day or do night audit, all the bills along with the amount and bill number should be automatically credited to one of my GL Accounts which I can map. So just want to know the details of mysql and how should I do (offcourse just back end). Plus I would also like to have GL Account list to be displayed in my software to select the account to  which bill amount will be credited. The whole Idea is that when guest check's out,  accountant doesn't have to reenter the bills and all the details say for example laundry, beverages, room charge automatically gets credited to FA. So i'll be needing the code for displaying the GL account list and to which all table should I insert the bill amounts.
Example:
1> If I define a new room in my software I should get a list of GL Accounts asking me where to credit this sale to.  So code for displaying Accounts is needed.( In this case I'll open new GL Acc from FA called "Room Sales" and associate rooms with this Acc)
2> When I roll over the day, my php script checks the ID for the selected GL Account  and inserts the bill id and amount to the FA database containing records for that particular GL Account. (Suppose 2 guest have checked out today so at night 12, I'll roll over the day so my php script checks the ID of the GL Acc associated with that room and will insert in to database or table containing all records for sales, bill id and amount automatically), but i'll be also needing info if any other table keeps the record of the same....

So I'll be grateful to you if you help me.

Note: php and mysql is the technologies I am using.