My website doesn't "recognize" my database on localhost

I'm creating a website on localhost using Xampp and PhpMyAdmin to create a db. When I try to use my function to subscribe with username and password, it seems that the db doesn't work: my site displays me that accepted the input but in the user table on phpMyAdmin I can't find the new user just added. I don't know if the problem is the query or the connection to db itself. Is there away to debug it? Sorry for my bad English