如何在单击下拉菜单中更改mysql的文本框值

Question

I am at the very basic level of coding and I need help regarding this. You can post other links if there are any, related to this thing.

I want to get values from database dynamically on selection of city drop down and set it in a text box.

Any help will be appreciated.!!

enter image description here

<tr>
    <td>
        <label>City</label>
    </td>
    <td>
        <select id="state" name="city" class="form-control" >
        <?php 
            $sql = "SELECT city FROM service_point GROUP BY city";
            $sel = mysql_query($sql);
            // output data of each row
            while($row = mysql_fetch_array($sel)) {
                $city=$row['city'];
        ?>
                <option value="<?php echo $row['city'] ?>">
                    <?php echo $row['city']; ?></option>
            <?php }?>
        </select>
    </td>
    </select>
</tr>
<tr>
    <td>&nbsp;</td>
</tr>
<?php 
include('config.php');
$s_name="";
$address="";
$phone_no="";
$email="";
$cperson="";
$city="";
$id=$_POST['city'];
$sql = "SELECT * FROM service_point where city = $id'' ";
$query = mysql_query($sql);
echo $sql;
while($row = mysql_fetch_array($query)){ 
?>
<tr>
    <td> Name Of Service Point</td>
    <td><input type="text" name="name" value="<?php echo $row['s_name'];?>"/></td>
</tr>
<tr>
    <td>&nbsp;</td>
</tr>
<tr>
    <td>Address </td>
    <td><textarea name="address" col="5" value="<?php echo $row['address'];?>"></textarea></td>
</tr>
<tr>
    <td>&nbsp;</td>
</tr>
<tr>
    <td>Phone No</td>
    <td><input type="text" name="phoneno" value="<?php echo $row['  phone_no'];?>"/></td>
</tr>
<tr>
    <td>&nbsp;</td>
</tr>
<tr>
    <td>Email Id</td>
    <td><input type="text" name="email" value="<?php echo $row['email'];?>"/></td>
</tr>
<tr>
    <td>&nbsp;</td>
</tr>
<tr>
    <td>Contact Person</td>
    <td><input type="text" name="cperson" value="<?php echo $row['cperson'];?>"/></td>
</tr>
<tr>
    <td>&nbsp;</td>
</tr>
<tr>
    <td></td>
    <td align="center"><input type="submit" name="submit" value="submit"/><td>
</tr>
</table>
<?php }?>
</form>

</div>