php - Grouping Results from database -

i trying display results in category's based on id information data base creates category header on again.

for example:

title category demo cat 1
topic 1 cat 1

title category demo cat 1
topic 2 cat 1

title category demo cat 2
topic 3 cat 2

when should display:

title category demo cat 1
topic 1 cat 1

topic 2 cat 1

title category demo cat 2
topic 3 cat 2

<table class="table table-bordered table-hover">     <?php  $sql = "select * forums, forum_categories forum_categories.cat_id = forums.cat_id order forum_categories.cat_id"; $result = query($sql);  while (($row = mysqli_fetch_assoc($result)) != false) {      $cat_id = $row['cat_id'];         $cat_title = $row['cat_title'];      echo "<thead>";              echo "<tr>";                  echo "<th colspan='4'>$cat_title</th>";             "</tr>";          echo "</thead>";          echo "<tbody>";       $forums_cat_id = $row['cat_id'];     $forum_name = $row['forum_name'];      $forum_desc = $row['forum_desc'];     $forum_last_post_id = $row['forum_last_post_id'];      echo "<tr>";      echo "<td>$forums_cat_id</td>";     echo "<td>$forum_name<br>$forum_desc<br>admin</td>";     echo "<td>0</td>";     echo "<td>0</td>";       echo "</tr>"; }  ?>        </tbody> </table> 

you printing header each result mysql returns, each row. you're not distinguishing whenever "new" category found. can done simple creating temporary variable array. example:

$displayedcategories = array();  while (($row = mysqli_fetch_assoc($result)) != false) {     if (!in_array($row['cat_id'], $displayedcategories)) {         // new category, display , save in $displayedcategories         $displayedcategories[] = $row['cat_id'];         echo "<thead>";         echo "<tr>";         echo "<th colspan='4'>$cat_title</th>";         echo "</tr>";         echo "</thead>";     }      // other stuff here... } 

this way, "new" category that's not encountered, header printed once , category id saved $displayedcategories array. if same category encountered again, header not output again.