How do I make my html <select> sticky with php?

Question

I have been trying to make my select sticky so that it will retain the value of the firstname and lastname of the user that is currently being searched. I have tried many approaches including structuring my php differently so that the script is at the beginning of the file and starts with if(isset($_POST['submit'])){} then it echoes the html with the fields filled out and else{} echo the html blank. This approach below is the closest I have gotten to making it sticky I think but I still can't get it to work.

<?php

$user_id = 2;
$user_firstname = "Soren";
$user_lastname = "Craig";
require ('mysqli_connect.php');

# based on student name, get list of files uploaded 
$pageTitle = "View User Files";
include ('includes/header.html');
?>

<div class="container">
  <h2>Uploaded Files</h2>
    <div class="form-group col-xs-4">
        <form action="newview.php" method="POST">
        <label for="sel1">Select User:</label>
        <select class="form-control" id="select-user" name="select-user">
            <option><?php if(isset($firstname) &&  isset($lastname)) echo $lastname . ", " . $firstname?></option>
  <?php
  $query = "SELECT user_id, firstname, lastname FROM studentusers ORDER BY lastname ASC";
  $stmt = mysqli_prepare($dbconnect, $query);
  if(mysqli_stmt_execute($stmt))
  {
    mysqli_stmt_bind_result($stmt, $user_id, $firstname, $lastname);
    while(mysqli_stmt_fetch($stmt))
    {
      echo '<option value="' . $user_id . '">' . $lastname . ", " . $firstname . "</option>";
    }
  }

  echo "</select>";
  mysqli_stmt_close($stmt);

         echo '<button type="submit" name="submit" class="btn btn-primary">Submit</button>
    </form>';

if(isset($_POST['submit']))
{
    $user_id = $_POST['select-user'];

    echo '<p>' . $firstname . " " . $lastname . '</p>            
  <table class="table table-hover">
    <thead>
      <tr>
        <th>Name</th>
        <th>Description</th>
        <th>Date</th>
      </tr>
    </thead>
    <tbody>';



$query = "SELECT filename, posteddate FROM fileuploads WHERE user_id = ?";
$statement = mysqli_prepare($dbconnect, $query);
mysqli_stmt_bind_param($statement, 'i', $user_id);
if(mysqli_stmt_execute($statement))
{
  // bind the result
  mysqli_stmt_bind_result($statement, $fileName, $fileDate);
  while(mysqli_stmt_fetch($statement))
  {
    echo "<tr>
            <td><a href='../uploads/'" . $fileName . "> " . $fileName  . " </a></td>
            <td></td>
            <td>" . date('F j, Y', strtotime($fileDate)) . "</td>
            </tr>";
  }

}

}

?>
</div>
</body>
</html>

Any help is much appreciated... Thanks!

Answer 1

You mean that after the form's submitted and re-displayed, you want the previous selected values to be already-selected in the form?

Easy enough:

while(...) {
   if (should be selected) {
       <option selected="selected">...</option>
   } else {
      <option>...</option>
   }
}