Select value from drop down list and display in text area, PHP.?

Im trying to get data from database after drop down list value is selected and display it in a text area.
I have this for now....

<div id="getFb">
<select name="natureOffb" class="selection">
<option value="Feedback">Feedback</option>
<option value="Enquiry">Enquiry</option>
<option value="Compliment">Compliment</option>

<?php
$sql=mysqli_query($mysqli, "SELECT natureOffb From forum");
while($row = mysqli_fetch_array($sql)){

}
?>

</select>
<br>
<textarea class="display"></textarea>
<textarea class="display"></textarea>
<textarea class="display"></textarea>
<textarea class="display"></textarea>
</div>

After that, Im lost/stucked. Help?

Thank you!