I'm assuming in the SELECT you remembered to actually replace "dbo" with the real database name? I was able to run the function as below through PhpMyAdmin and got a response from the function:
SELECT `DATABASE_NAME_HERE`.`random_text_answer`();
The user kanvull_main is assigned to the database, so while I can't test using that user easily, I see no reason it wouldn't work provided the database name is correct in the SELECT statement.