Q: Rails 3 Multiselect input param

In Rails 3, I have a multi-select form control (fig. 1). When I select
more than 1 value, Firefox sends both values (fig. 2). But only the last
value gets sent as a input value to my controller (fig. 3). How do I get
all those values passed on to my controller?

      <form action="html_items/search" method="post" >

        <!-- Criteria -->
        <div style="float:none;">
          <label>Content Provider </label>
          <select multiple id="content_provider"
            <option value="FLR">Flare</option>
            <option value="SLDT">Slashdot</option>

        <input type="submit" value="Search" />

fig. 1

content_provider FLR
content_provider SLDT
fig. 2

PARAMs[{"content_provider"=>"SLDT", "controller"=>"html_items",
fig. 3