how ican seperate thecategories of my forum

Code:
//start forums_div

echo '<div id="forums_div">  

      <table id="table_forums">

        <tr>

        <th class="tete">Nom forum</th>

        <th class="tete"> Discussion</th>

        <th class="tete"> Messages </th>

        <th class="tete">Dernier message</th>

         </tr>' ;

     

     

foreach($r as $l){



echo  '<tr>'; 

echo  '<td>'. anchor('forum/viewthreads/'. $l['forum_id'] ,$l['forum_name']) .'<br> ';

echo  $l['forum_desc'].'</td> ' ;

echo  '<td class="case">'  . $l['NbrDiscussion'] .'</td>'  ;

echo  '<td class="case">'  . $l['NbrMessage']    .'</td>'  ;

echo  '<td class="case">'  .$l['post_title'] .'<br>'.$l['reply_by'] .

.unix_to_human($l['post_date']) .'/td>'  ;

echo  '</tr>' ;

}



echo  '</table>';   //fin table de forum

echo     '</div>'  ;  //fin forums div