Dynamic mysql -> excel export - php

Question

First off all - a "normal" export and writing an Excel file using phpspreadsheet works like a charm.
What I can't find out is how to do this in a dynamic way.
"Dynamic" means not manually defining the headlines in row1 and not defining manually the data columns from mysql.
What I've done (tried):
$spreadsheet = new Spreadsheet();
$sheet = $spreadsheet->getActiveSheet();
$sheet->setTitle('test');
if ($result = $mysqli -> query($sql)) {
$co = 'A';
$ro = '1';
while ($fieldinfo = $result -> fetch_field()) {
// printf("$col.$row %s\n", $fieldinfo -> name);
$sheet->setCellValue($co.$ro, $fieldinfo -> name);
$$co = $fieldinfo -> name;
$co++;
}
$result -> free_result();
}
This creates an excel file with all field names like defined in the mysql view/statement.
The challenge is to put date in column by column without creating them by code.
What I've done is to generate a variable for each column. So $A = firstname, $B = name, etc.
My idea was to address this variable by something like "first column is 'A' then I've to address the variable $A. But dynamically call variables doesn't work somehow
$sheet->setCellValue($co.$ro, $row[$cuco]);
$cuco (current column) should be $cuco = '$'.$A, but then the value of $cuco will be $A and the resolved variable $A which should be "firstname" i.e.

Answer 1

What I've done is add a comment to each column in the database that corresponds to the heading I want for that column. An additional query will give you that data which you may then use to populate the header row.
Here's the function I use FWIW:
//
// Returns an array indexed by column names with the column comment,
// if any, as the value from the table name that is passed - columns
// that do not have a comment are not included in the returned array
//
public function get_column_comments($table) {
$ColsQ = $this->database->prepare('SHOW FULL COLUMNS FROM `' . $table . '`');
$ColsQ->execute();
$ColsD = $ColsQ->fetchAll(PDO::FETCH_ASSOC);
foreach ($ColsD as $col) {
if (empty($col['Comment'])) {continue;} // ignore columns without a comment
$cols[$col['Field']] = $col['Comment'];
}
return $cols;
} // end of get_column_comments function