PHP, MySQL, Array from HTML Form in Search Query?

I have a search engine with an html form that sends data to a PHP script the queries a MySQL database. In the html form, I have a option that allows multiple selections. Thus far, I have put square brackets after the name in the HTML in order to make it an array. But I think there is a problem in the PHP because results are not correct.

HTML

<select multiple="multiple" name='category[]'>
      <option>Literature</option>
      <option>History</option>
      <option>Science</option>
      <option>Fine Arts</option>
      <option>Trash</option>
      <option>Mythology</option>
      <option>Phylosophy</option>
      <option>Social Science</option>
      <option>Religion</option>
      <option>Geography</option>
  </select>

search.php

$button = $_GET ['submit'];
$search = $_GET ['search'];

}

if(strlen($search)<=1)
echo "Search term too short";
else{
echo "You searched for <b><em>$search</em></b> and ";
mysql_connect("fake","fake","fake");
mysql_select_db("quinterestdb");}

mysql_real_escape_string($search);

$search_exploded = explode (" ", $search);

foreach($search_exploded as $search_each)
{
$x++;
if($x==1)
$construct .="Answer LIKE '%$search_each%'";
else
$construct .="AND Answer LIKE '%$search_each%'";

}

$cat = $_GET ['category'];
$comma_separated = implode("','", $cat);

$constructs ="SELECT * FROM tossups WHERE $construct AND Category IN('$comma_separated')";
$run = mysql_query($constructs);

When I use the search engine, the script runs just fine, but there are still results that have categories that were not selected. Any idea?