<?php
foreach($db->query('SELECT * FROM table') as $row) {
  echo $row['field1'].' '.$row['field2']; //etc...
}

The query() method returns a PDOStatement object. You can also fetch results this way:

<?php
$stmt = $db->query('SELECT * FROM table');
 
while($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
  echo $row['field1'].' '.$row['field2']; //etc...
}

or

<?php
$stmt = $db->query('SELECT * FROM table');
$results = $stmt->fetchAll(PDO::FETCH_ASSOC);
// Use $results...

Note the use of PDO::FETCH_ASSOC in the fetch() and fetchAll() code above. This tells PDO to return the rows as an associative array with the field names as keys. Other fetch modes like PDO::FETCH_NUM returns the row as a numerical array. The default is to fetch with PDO::FETCH_BOTH which duplicates the data with both numerical and associative keys. It's recommended you specify one or the other so you don't have arrays that are double the size! PDO can also fetch objects with PDO::FETCH_OBJ, and can take existing classes with PDO::FETCH_CLASS. It can also bind into specific variables with PDO::FETCH_BOUND and using the bindColumn method. There are even more choices! Read about them all here: PDOStatement Fetch documentation.