PHP - while inside while in table - php

Question

I have a table that I want to assign a staff member to for each row. I want a dropdown on the last column with all the staff members so I can assign a staff member by clicking their username in the dropdown.
I'm trying to do a while loop inside a while loop but am getting an error.
This is my current code:
<table class="table table-bordered table-striped js-dataTable-full table-header-bg">
<thead>
<tr>
<th>Actions</th>
<th>Username</th>
<th>Service</th>
<th>Price</th>
<th>Date Ordered</th>
<th>Account Email</th>
<th>Account Password</th>
<th>Status</th>
<th>Assign to staff</th>
</tr>
</thead>
<tbody>
<?php
$clients_result = mysqli_query($con, "SELECT * FROM boosting_orders ORDER BY id ASC");
$query = mysqli_query( $con, "SELECT * FROM users" );
if(mysqli_num_rows($clients_result) > 0) {
while($payment_row = mysqli_fetch_array($clients_result)) {
echo '
<tr id="no_enter">
<td style="text-align: center;">
<div class="btn-group">
<a class="btn btn-xs btn-default" type="button" data-toggle="tooltip" title="" data-original-title="Edit Order" href="orders_admin?action=edit&identification='.$payment_row['id'].'"><i class="fa fa-pencil"></i></a>
<a class="btn btn-xs btn-default" type="button" data-toggle="tooltip" title="" data-original-title="Remove Order" href="orders_admin?action=delete&identification='.$payment_row['id'].'"><i class="fa fa-times"></i></a>
</div>
</td>
<td>
'.$payment_row['users_name'].'
</td>
<td>
'.$payment_row['service'].'
</td>
<td>
$'.$payment_row['price'].'
</td>
<td>
'.$payment_row['date_ordered'].'
</td>
<td>
'.$payment_row['email'].'
</td>
<td>
'.$payment_row['password'].'
</td>
<td>
'.($payment_row['status'] == 'Completed' ? '<span class="label label-success" data-toggle="tooltip" title="" data-original-title="Your account has successfully been boosted">Completed</span>' : '<span class="label label-info" data-toggle="tooltip" title="" data-original-title="This order is either still pending or corrupt">Pending</span>').'
</td>
<td>
<select name="assign_staff" class="form-control">
'. while($row = mysqli_fetch_array($query)) { .'
<option value="'.$row['username'].'">'.$row['username'].'</option>
'. } .'
</select>
</td>
</tr>
';
} } else { } ?>
</tbody>

Answer 1

you can't concatenate string with while syntax,
the code in the last <td> should be:
echo '<select name="assign_staff" class="form-control">';
while ($row = mysqli_fetch_array($query)) {
echo '<option value="' . $row['username'] . '">' . $row['username'] . '</option>';
}
echo '</select>