PHP MySQL Loop on two-level data

Question

I am trying to extract two layer data from mysql database with a single mysql query and then display it grouped by top-layer with a php while loop.

<?php $org = "1";

$row1 = mysqli_prepare($db,"SELECT * FROM menu WHERE org = ? ORDER BY mid DESC"); 
$row1->bind_param("s", $org);
mysqli_stmt_execute($row1); $row2 = mysqli_stmt_get_result($row1);

while($row = mysqli_fetch_array($row2)){ ?>

<div class="category"><?php echo $row["item"]; /* GROUPED*/?>
<div class="item"><?php echo $row["item"]; /* INDIVIDUAL ITEM*/?></div>
</div>

<?php }; ?>

mid	parent	org	item	price
1		1	Category 1
2	1	1	Item 1	$10
3	1	1	Item 2	$12
4		1	Category 2
5	4	1	Item 3	$12
6	4	1	Item 4	$90

Obviously each item will appear only once but also the category will appear as many times as the underlying items. In the code however i need to group all items under the same parent category. Any ideas?

Desired Result

List
Category 1
- Item 1
- Item 2
Category 2
- Item 3
- Item 4

Or in terms of the HTML code output:

<div class="category">Parent Category 1<br>
<div class="item">Item 1</div>
<div class="item">Item 2</div>
</div>
<div class="category">Parent Category 3<br>
<div class="item">Item 3</div>
<div class="item">Item 4</div>
</div>

Answer 1

This should do it;

SELECT          T.*, 
                IF(T.parent IS NULL, T.mid, T.parent) AS ParentGroup
FROM            mytable as T
WHERE           T.org = 1 # Comment out here to get for all org
ORDER BY        T.org ASC, ParentGroup ASC, T.parent IS NULL DESC, T.mid ASC

Note: Please read the SQL injection policies carefully before using SQL statements with your code.

I hope you already know how to fetch data with PHP from MySQL; once all records are fetched, you can loop through like below;

... Here you already fetched all the records from database into $Recordset array

foreach($Recordset as $Data){ // Loop through the record set
    if($Data["parent"]){
        print "<li>{$Data["item"]}</li>"; // Item
    }
    else{
        print "<div class=\"Category\"><h1>{$Data["item"]}</h1><ul class=\"Item\">"; // Category
    }
}

print "</ul></div>";

Answer 2

Add flow control to your code

<?php 
$org = "1";

$row1 = mysqli_prepare($mysqli,"SELECT * FROM menu WHERE org = ? ORDER BY mid ASC"); 
$row1->bind_param("s", $org);
mysqli_stmt_execute($row1); 
$row2 = mysqli_stmt_get_result($row1);
$controlfirst = 0;
while(  $row = mysqli_fetch_array($row2)) {
    if ( !isset($row["parent"])) { 
        if ( $controlfirst == 1) {  ?>          
        </div> 
    <?php } ?>
        <div class="category"><?php echo $row["item"]; /* GROUPED*/ 
     $controlfirst = 1;
    }
    else { 
            ?>
            
            <div class="item"><?php echo $row["item"];?> </div>/* INDIVIDUAL ITEM*/
    <?php  }
 }      
if ( $controlfirst == 1) {  ?>      


    </div> 
<?php } ?>

See example