Yes, you can use variables for the index values of an array. For example,
$row = array('col_name' => 'column value');
$index = 'col_name';
echo $row[$index]; // Equivalent to $row['col_name']. Prints "column value"
You should be able to accomplish what you want pretty easily using the above logic. Basically just store the column names from the first query into an array, then loop through that array to get the column names each time you print a row.
Give this a try:
// Display all sqlite column names for chosen table
$db = new SQLite3('data.db');
$tablesquery = $db->query("PRAGMA table_info(USERS)");
$columns = array();
while ($table = $tablesquery->fetchArray(SQLITE3_ASSOC)) {
$columns[] = $table['name'];
}
// Display * from USERS
$db = new SQLite3('data.db');
$results = $db->query('SELECT * FROM USERS');
while ($row = $results->fetchArray()) {
foreach ($columns as $col)
echo $col . " = " . $row[$col] . "\n";
}