Display all information from table?

PHP Newbie here, How do I automate the display of all information given a freeform SQL Query and db name? Im trying to create a simple PHP3 page in which I can choose database to perform query on, and just enter a freeform SQL query (e.g. SELECT * from accounting WHERE user="gumby") From all I have seen, you typically specify the column names in that particular table. But since I want the ability to choose from any table, this wont work. Any help is greatly appreciated! Thank you in advance.