title: Sql, Object vs String/Array
body: <p>Why does this produce an object?</p>
  
  <pre><code>$sql = $this-&gt;db-&gt;query("
    SELECT 'product_id'
    FROM " . DB_PREFIX . "product_to_category
    WHERE category_id = '" . $this-&gt;db-&gt;escape($category['category_id']) . "'
  ");
  </code></pre>
  
  <p>And how to I get a string/array instead?</p>
  
  <p>From Opencart
  Related: Object of class stdClass could not be converted to string</p>