display binary tree with php -

i have table this

id(ai)  user_id parent_user_id zone_id  1        8          0         0  2        8_l        8         l  3        8_r        8         r    

and on want display binary tree,a nd use recursive function.,but seems not given correct put

code

 <div id='all' style='width: 250px;' align="center">8 <?php //childnode(1); function childnode($id) { global $wpdb;  $prefix=$wpdb->prefix;        $check_parent_node= $wpdb->get_results( $wpdb->prepare("select * ".$prefix."user_reference parent_user_id =".$id." limit 2" ));      $user_count = $wpdb->get_var( "select * ".$prefix."user_reference parent_user_id =".$id." limit 2" );     //select * ".$prefix."user_reference parent_user_id =".$id." limit 2     //var_dump($user_count);     if($user_count>0)     {         echo "<div>";          foreach($check_parent_node $chkpn)         {             if($chkpn->zone_id == 'l')             {                 echo "<div id='left'style='float:left'>";                 echo $chkpn->user_id ."&nbsp&nbsp&nbsp";             }             else             {                 echo "<div id='rigth' style='float:right'>";                 echo "&nbsp&nbsp&nbsp".$chkpn->user_id;             }             childnode($chkpn->user_id);             echo "</div>";         }         echo "</div>";      } }   global $wpdb; $prefix=$wpdb->prefix;  $user_parent_ids = $wpdb->get_results( $wpdb->prepare("select * wp_user_reference " ));                  $parent_ids_array; $count=0;     foreach($user_parent_ids $urd) {    $parent_ids_array[$count]=$urd->parent_user_id;    $count++;  }     $unique_parent_ids_array = array_unique($parent_ids_array);   foreach($unique_parent_ids_array $upa)  {  if($upa!=0){  childnode($upa);     //echo "<br>".$upa."<br>";  }  }  ?> 

and out put im getting

8 

8_l 8_r 23_l 23_r 24_l 24_r 25_l 25_r 26_r26_l
27_l 27_r 28_l 28_r 29_l 29_r 30_l 30_r 31_l 31_r 32_l 32_r