PHP MySQL Loop on two-level data

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>

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