find column names from query

Hello,
I'm trying to find a way to get the column names of a table, knowing only the table name. (I'm trying to display the contents of various hidden support tables to the DB administrator)

here's what's happening:
user picks a table name from a select list (HTML),
a SELECT * FROM selected_table ... query is sent (PHP)
nested for loops print out the table data (PHP and HTML)
works great to here, although I realize I'm cheating a little.
problem is the data has no column labels.

going through the documentation I found the following:

SELECT attname::regclass FROM pg_attribute WHERE attrelid = travel::regclass

I'm trying to get the attname, which should be the column name, from the pg_attribute "table"(or catalog?) when attrelid, which should be the table name, which I have.

trying this query in PgadminIII I get:
ERROR: cannot cast type name to regclass

I could go through and hardcode the table data into the application, but I'd prefer not to.

Any suggestions to make this work, or for better methods appreciated.
Ray