php display data in div, h1, ul using while loop - php

Question

I am not very good in php and mysql but based on my code, I am able to display the results that I wanted but, it is not displaying in the right DOM structure.
I would like to display like below:
<div class="container">
<h1>Header</h1>
<ul><li>
<p>data 1</p>
<p>data 2</p>
</li></ul>
</div>
<div class="container">
<h1>Header</h1>
<ul><li>
<p>data 1</p>
<p>data 2</p>
</li></ul>
</div>
I have no idea why my code keep returning me the data and display everything in the 1st level ul instead of separating like below:
<div class="container">
<h1>Header</h1>
<ul><li>
<p>data1</p>
<p>data 2</p>
<div class="container">
<h1>Header</h1>
<ul><li>
<p>data1</p>
<p>data 2</p>
</li></ul>
</div>
</li></ul>
</div>
I have played around with the code and tried different ways but still unable to get it display properly. Below is my code:
<?php
$data='';
$previousVal = '';
// Update new images
$levelArray=array('B1','L1','L2','main','L3','L4','L5');
foreach ($levelArray as $i=>$level) {
$img = "img/".$level.".jpg";
if($level=='main'){
$result = mysqli_query($con,"SELECT * FROM floor_directory ORDER BY categories");
}
else {
$result = mysqli_query($con,"SELECT * FROM floor_directory WHERE level='$level' ORDER BY categories");
}
while($row = mysqli_fetch_array($result)){
if($previousVal != $row['categories']){
$data .= '<div class="container"><h1>'.$row['categories'].'</h1>';
$previousVal = $row['categories'];
}
$data .= '<ul><li>
<p class="float_left">'.$row['name'].'</p>
<p class="float_right">'.$row['unit_number'].'</p>
</li></ul></div>';
}
if($levelArray[$i]=='main'){
echo '<div class="swiper-slide">
<img src="'.$img.'" alt="" />
<div class="content_container_main">'.$data.'</div>
</div>';
}
else {
echo '<div class="swiper-slide">
<img src="'.$img.'" alt="" />
<div class="content_container">'.$data.'</div>
</div>';
}
$data='';
$previousVal = '';
}
?>
Hope you guys understand. Thanks in advance for the help guys.

Answer 1

changing code in while will make it work, change this code,
while($row = mysqli_fetch_array($result)){
if($previousVal != $row['categories']){
$data .= '<div class="container"><h1>'.$row['categories'].'</h1>';
$previousVal = $row['categories'];
}
$data .= '<ul><li>
<p class="float_left">'.$row['name'].'</p>
<p class="float_right">'.$row['unit_number'].'</p>
</li></ul></div>';
}
with this,
while($row = mysqli_fetch_array($result)){
if($previousVal != $row['categories']){
$previousVal = $row['categories'];
}
$data .= '<div class="container"><h1>'.$row['categories'].'</h1>';
$data .= '<ul><li>
<p class="float_left">'.$row['name'].'</p>
<p class="float_right">'.$row['unit_number'].'</p>
</li></ul></div>';
}
you may even remove the if check (inside while loop) if not using in further script.