TwoFactorAuth | PHP library for Two Factor Authentication | Authentication library

To answer your question in general - yes, you can put a helper function in the same file where sql connection is made.

However, the code of your actual function is questionable at the very least. Or, to tell you truth, your function selectdb() is a torture for a programmer and shouldn't be stored anywhere. Stick to natural SQL queries written as is. You don't need numbers to represent tables. You don't need $rows variable. Everything could be written right in the SQL string. All you will need is a simple helper function that would reduce the amount of code required to run a query.

Here is an example of such mysqli include file

Once it's included in in your script, you can use it to run any mysql query, to any table, with any list of variables. Check out the following example (you can copy and paste the following code block to your file and run it as is):