//index.php
<script type="text/javascript">
$(document).ready(function()
{
$(".autodoc").change(function()
{
var id=$(this).val();
var dataString = 'id='+ id;
$.ajax
({
type: "POST",
url: "ajax_price.php",
data: dataString,
cache: false,
success: function(html)
{
$(".pay").html(html);
}
});
});
});
</script>
.
.
<form action="bill_submit.php" method="POST"  id="bbe">
<input type="text" name="name" id="textfield2" class="input-xlarge" data-rule-required="true" data-rule-minlength="1" placeholder="Name" maxlength="30">
<input type="text" name="med" id="keyword" tabindex="0" class="autodoc">
.
.
</form>

//ajax_price.php

<?php
include('db_conn.php');

if ($_POST['id']) {
$id    = $_POST['id'];
$query = "select * from pharma where name='$id' ";
//echo $query;
$result = mysqli_query($con, $query);

if (mysqli_affected_rows($con) != 0) {
    while ($row = mysqli_fetch_array($result, MYSQLI_ASSOC)) {
        echo "<input class='txt' type='text' value ='" . $row['per_unit_price'] . "' name='txt' id='fbname' readonly/>";

    }

} else {
    echo "<input class='txt' type='text' value ='$name' name='txt' id='fbname' readonly/>";
}

}
?>