Keep values in <select> for loop after submit - php

Question

I am trying to retain the values in my select with a for loop option if form is submitted incomplete. It inserts the values into database and functions perfectly fine but I don't want people to have to fill out all the for loop selects again if they submit the form incomplete.
if(!empty($_POST['height'])){
$height = $_POST['height'];
}
<select class="form-control selectpicker" name="height">
<option value="" disabled selected>Select Your Height</option>
<?php
for ($i=1; $i<=250; $i++)
{?>
<option value="<?php echo $i;?>"><?php echo $i;?>cm</option>
<?php
}
?>
</select>
I have my other select functioning perfectly:
<?php
if(isset($_POST['city'])){
$city = $_POST['city'];}?>
<select class=" form-control selectpicker" name="city" value="">
<optgroup label="Thailand">
<option disabled selected>Select A City</option>
<option
<?php
if (isset($city) && $city=="Bangkok") echo "selected";?>
>Bangkok</option>
<option <?php
if (isset($city) && $city=="Phuket") echo "selected";?>
>Phuket</option>
<option <?php
if (isset($city) && $city=="Pattaya") echo "selected";?>
>Pattaya</option>
</optgroup>
</select>
Essentially I want to achieve the same result as the City select but with the for loop in the Height select.
I have spent the last couple of days researching and trying to implement different codes and strategies to make it work but I still can't get it to function. Any help is greatly appreciated and if there is anymore code or explanation required I will be happy to provide it.

Answer 1

You have added value in $height. But in select, you haven't use it to retain selected value. change your drop-down for height as below-
if(!empty($_POST['height'])){
$height = $_POST['height'];
}
<select class="form-control selectpicker" name="height">
<option value="" disabled selected>Select Your Height</option>
<?php
for ($i=1; $i<=250; $i++)
{?>
<option value="<?php echo $i;?>" <?php if (isset($height) && $height==$i) echo "selected";?>><?php echo $i;?>cm</option>
<?php
}
?>
</select>