I am looking for advice how to merge authentication of two php /mysql scripts developed by two authors so that user need not login to each of them independently - logging into one takes to the other without additional login. Both scripts will be on same domain and db.
This will require modifying the source code and database for both applications and then developing a new central login system - which will need an experienced developer to accomplish.
If you don’t have experience with PHP development, you may want to check Envato Studio for freelancers who can do this for you.
Otherwise, you’ll want to contact the authors for advice since we cannot see the source code of the items here. Though, bear in mind, the authors are not required to advise or help you with this.