根据下拉列表中的选定值从数据库填写表单值

Question

I've a form like this and if the user selected any value from the dropdown then I want to fetch the details from the database based on that value. Suppose say if the user selected Name 2 from the dropdown then I should automatically fill the fields address & phone that are relevant to Name 2. Also I'm unable to get the value $_POST['name']. I've tried but no luck. Here is my code. Please suggest me if is there any other way to achieve it. Thank you.

HTML

<select id="name" name="name">
    <option value="1">Name 1</option>
    <option value="2">Name 2</option>
    <option value="3">Name 3</option>
    <option value="4">Name 4</option>
    <option value="5">Name 5</option>
</select>

<input type="text" name="address" id="address" />
<input type="text" name="phone" id="phone" />

jQuery

$(document).ready(function () {
    $('#name').change(function(){
        var name = $(this).val();
        var dataString = "name=" + name;
        alert (dataString);
        $.ajax ({
            type: "POST",
            url: "test.php",
            data: dataString,
            dataType: json,
            success: function(data) {
                $('#address').val(data.address);
                $('#phone').val(data.phone);
            }
        });
    });
});

PHP

<?php

ini_set('display_errors',1); // enable php error display for easy trouble shooting
error_reporting(E_ALL); // set error display to all

include "connect.php";

if (ISSET($_POST['name'])) {

    $ref = $_POST['name'];

    $query = $con->query("SELECT * FROM test WHERE id = '$ref' LIMIT 1");
    $row = $query->fetch_assoc();

    $address = $row['address'];
    $phone = $row['phone'];

    $json = array('address' => $address, 'phone' => $phone);
    echo json_encode($json);
}

$con->close();
?>

Answer 1

HTML

<form>
<select id="name" name="name">
    <option value="1">Name 1</option>
    <option value="2">Name 2</option>
    <option value="3">Name 3</option>
    <option value="4">Name 4</option>
    <option value="5">Name 5</option>
</select>
</form>

<input type="text" name="address" id="address" />
<input type="text" name="phone" id="phone" />

jQuery

$('#account_head').change(function(){
    var name = $(this).val();
    var dataString = "name=" + name;
    $.ajax ({
        type: "POST",
        url: "get_results.php",
        data: dataString,
        dataType: 'json',
        success: function(data) {
            // console.debug(data);
            $('#agent').val(data.agent);
            $('#tin').val(data.tin);
            $('#address').val(data.address);
        }
    });
});

PHP

<?php
if (ISSET($_POST)) {
    $ref = $_POST['name'];

    $query = $con->query("SELECT * FROM test WHERE id = '$ref' LIMIT 1");
    $row = $query->fetch_assoc();

    $address = $row['address'];
    $phone = $row['phone'];
    $json = array('address' => $address, 'phone' => $phone);
    echo json_encode($json);
}
?>