dropdown select value resets after onchange - php

Question

I am trying to create a dynamic drop-down using php/mysql. For some reason the selected value does not stay selected. The drop-down reset to the initial value. The selected value is used to populate a table on the same php page.
<form action="" method="get">
<select name="user" onchange="this.form.submit();">
<?php
do {
?>
<option value="<?php echo $row["userid"]?>" selected="selected"><?php echo $row["display_name"]?></option>
<?php
} while ($row = mysqli_fetch_assoc($result));
$rows = mysqli_num_rows($result);
if($rows > 0) {
mysqli_data_seek($result, 0);
$row = mysqli_fetch_assoc($result);
}
?>
</select>

Answer 1

You have to add a logic in your code for that.
First when you get data from form, save your dropdown value in a variable.
eg. $user = $_GET['user'];
Now make the following changes in your code.
<form action="" method="get">
<select name="user" onchange="this.form.submit();">
<?php
do {
?>
<option value="<?php echo $row['userid']?>" <?php if($user == $row['user_id']) { echo 'selected="selected"' } ?> >
<?php echo $row["display_name"]?></option>
<?php
} while ($row = mysqli_fetch_assoc($result));
$rows = mysqli_num_rows($result);
if($rows > 0) {
mysqli_data_seek($result, 0);
$row = mysqli_fetch_assoc($result);
}
?>
</select>