Array#to_xml accepts :root_attrs

You can define root attributes using :root_attrs option:

@projects.to_xml(:root_attrs => {:page => 1, :per_page => 3})

<?xml version="1.0" encoding="UTF-8"?>
<projects page="1" per_page="3" type="array">
  <project>
    <name>project 1</name>
  </project>
  <project>
    <name>project 2</name>
  </project>
  <project>
    <name>project 3</name>
  </project>
</projects>

This is useful for paginated XMLs