fill fields of a form with data from a mysql bd when selecting a select

the idea is that by clicking on any option of a select depending on this I fill in the fields of my form I am working with php, mysql: this is my select

<select name="ruta" id="ruta" class="form-control" onchange="showService(this.value)">
        <?php 
          $link = mysqli_connect("localhost", "root", "");
          mysqli_select_db($link, "stp17");
          $tildes = $link->query("SET NAMES 'utf8'"); //Para que se muestren las tildes correctamente
          $result = mysqli_query($link, "SELECT * FROM rutas");
          while ($filas = mysqli_fetch_array($result)){
            ?>
            <option value="<?php echo $filas['id']; ?>"><?php echo $filas['nomCorto']; ?></option>
            <?php                 
          }
          mysqli_free_result($result);
          mysqli_close($link);
        ?>
      </select>

In this div

<div id="nomCorto"></div>

alamaceno the data but I do not know how to put them in text boxes

Script

function showService(str) {
if (str=="") {
  document.getElementById("nomCorto").innerHTML="";

  return;
}
if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
}
else {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function() {
  if (xmlhttp.readyState==4 && xmlhttp.status==200) {
    document.getElementById("nomCorto").innerHTML=xmlhttp.responseText;
  }
}
xmlhttp.open("GET","getservice.php?service="+str,true);
xmlhttp.send();

}

and this is my php file

    <?php
$link = mysqli_connect("localhost", "root", "");
   mysqli_select_db($link, "stp17");

$service = $_GET['service'];

$query = mysqli_query($link,"SELECT * FROM rutas WHERE id = '".$service."'");


while($row = mysqli_fetch_array($query)) {
?>
<p><?php echo $row['descripcion']; ?></p>
<?php
}

echo "</table>";

mysqli_close($link);
?>