Fix invoicing in PHP portal, add invoicing module

The previous developer scammed us. We have a tutoring management software that was created on PHP. It has issues, there is an invoicing section built in, but it is not properly connected to the hours bought by clients, and the hours logged by tutors. Everything has to be interconnected, like packages has to be connected with invoice , and invoice generation has to be connected with session generated. HOW IT HAS TO WORK: -Tutors log hours for their assigned student -Student gets an email notification every time a tutor logs a session. -At the end of the month we view all 'active' students that had hours logged and an automatic 'draft' invoice is made up for the hours they received. Any editing required is completed, and invoices are sent to student email. -List of pay owed to tutors also generated based on monthly logging -Student invoices have to be balanced between pre purchased hours, if they bought a package beforehand, or a more expensive hourly rate if they did not. -Any coupon codes or discounts that the client has are entered at check out and applied -All data is complied and sent to a reports tab -Sent invoices are not sorted in a list of invoices sent out to check who has paid and re-send to unpaid clients -Clients login on their end "pay invoice" online, developer must check if that is functioning (it should be), and if they send in payment by a manual way, admin updated on admin side. I have attached a video tour of what we have now. First you get to see the ADMIN view, then the TUTOR view and then the STUDENT view. We need to finalize everything to do with invoicing, make sure everything ties in and calculates properly. Deducts hours properly, charges students properly, and calculates pay for tutors properly. Invoices sent out have to look nice, be in a nice format, easy to edit before and after, easy to revise, be generated automatically and not sent until approved. All invoices for the month to appear in one easy to manage list. The majority of this portal is done. A lot of what has to be done is already there, it needs to be tied in, connected etc.