How to retain Select option after submitting the form in php - php

Question

I looked at several community forums, and I am unable to figure it out on how to retain select option value after validation fails.
Here is the code that works for me, but values disappear when submit button is submitted.
<select id="service" name="service" class="searchoption">
<option value="">-- Select Service Name --</option>
<?php
$resultservice = mysqli_query($con,"Select * from services") ?>
<?php
while ($line = mysqli_fetch_array($resultservice)) {
?>
<option value="<?php echo $line['serviceid'];?>"> <?php echo $line['service'];?> </option>
<?php
}
?>
</select>
Here is what I tried and doesn't work for me:
<select id="service" name="service" class="searchoption">
<option value="">-- Select Service Name --</option>
<?php
$resultservice = mysqli_query($con,"Select * from services") ?>
<?php
while ($line = mysqli_fetch_array($resultservice)) {
?>
<option value="<?php echo $line['serviceid']; if ($_POST['service'] == $service) {echo 'selected="selected"'} echo $line['serviceid']; ?>"> <?php echo $line['service'];?> </option>
<?php
}
?>
</select>

Answer 1

<form action="" method="POST">
<select name="list" id="list">
<option value="item1">item1</option>
<option value="item2">item2</option>
<option value="item3">item3</option>
</select>
<input type="submit" />
</form>
<script type="text/javascript">
document.getElementById('list').value = "<?php echo $_POST['list']?>";
</script>

Answer 2

May be a small error but noticed a invalid > in the following code
<option value="<?php echo $line['serviceid']; if ($_POST['service'] == $service) {echo 'selected="selected"'} echo $line['serviceid']; ?>"> <?php echo $line['service'];?> </option>
Try this
<option value="<?php echo $line['serviceid']; if ($_POST['service'] == $service) {echo 'selected="selected"'}?> echo $line['serviceid']; <?php echo $line['service'];?>" </option>
hope this helps