Creating a CSV file without every column heading

This is the code that I'm using to create a csv file based on a query:

$fp = fopen('spreadsheets/voter_not_validated.csv', 'w');
// we capture the structure in order to catch the field names
$headings=array();
$bruce_query = "DESCRIBE registration";
$bruce_recordset = mysqli_query($cxn, $bruce_query)
or die ("Couldn't excute query.");
while($bruce_row=mysqli_fetch_assoc($bruce_recordset)) {
    $headings[ ]=$bruce_row['Field'];
}
fputcsv($fp, $headings, ',', '"'); // this save the headings whether you have data  or not.

$bruce_query = "select * from registration WHERE registration_type <> 'fan' AND (voter_validation='' OR voter_validation=' ') AND
songwriting_contest BETWEEN '2011-03-01' AND '2011-12-31' order by first_name";
$bruce_recordset = mysqli_query($cxn, $bruce_query)
or die ("Couldn't excute query.");
while($bruce_row=mysqli_fetch_assoc($bruce_recordset)) {
    fputcsv($fp, $bruce_row, ',', '"');
}
fclose($fp);
echo "voter_not_validated.csv is created<BR>";

The great news is that it works wonderfully, however...

I want to create a csv file that only includes those columns that are relevant to the query. How do I initiate my csv file in a way where I'm not having to include all the columns in the original database? Right now, the "describe" dynamic, while it's working, is overkill and I'm having to doctor the resulting file a little bit before I can use it the way that I need to.

How do you create the csv file so it only has those columns that are referenced in the query as opposed to every column in the table sitting in the database?