如何在多个文本框中发布值

I had here a ajax function for posting data in pr field. What I need to do is post all the value base on pr# in my database. How I can post the other data in different textboxes using ajax? Below is my database structure and image and codes. Any help will be appreciate.

Pr Database Details Structure

Pr #  | Supplier  | Receipt #  | Receiver  |
--------------------------------------------
321-B | Villman   | 312312331  | John      |
556-B | Dockers   | 903232317  | William   |

Here's my Code

index.php

<select id="pr">
<?php ... ?>
</select>

<input id="pr_num">
<input id="supplier">
<input id="receipt">
<input id="receiver">

<script type="text/javascript">
$(document).ready(function()
{
$('input[id="pr"]').change(function()
{
var prjt_code = $("#pr").val();
$.ajax({
type: "POST",
url: "ajax.php",
data :"pr_code="+pr_code,
dataType:'html',
type:'POST',
   success:function(data){
  //alert(data);
    $('#pr_num').val(data);
   }
  });
return false;
});
});
</script>

Ajax.php

<?php
if(isset($_POST['pr_code'])) {
$pr_code= $_POST['pr_code'];

$sql = $mysqli->query("SELECT * FROM pr_table WHERE pr='$pr_code'");

while($row = $sql->fetch_assoc())
  {
  $code = $row['pr'];
  }
echo $code;
}
?>

You could add a class name for the pr_num textbox. let's say

<input type="text" id="pr_num" class="pr_num_class"/>

Then to iterate the textboxes use jQuery's .each() function

$(".pr_num_class").each(function(){
    $(this).val("//your text here");
})