contoh ajax

<?php
/*
saat di test.. hasilnya berhasil
kl gagal check dgn inspect element
*/
if(isset($_GET['id'])){
//==asumsikan sudah dapat nilainya
    $result=array(
       'nama'=>'test nama',
       'alamat'=>'alamat tes',
       'nomor'=>$_GET['id'], //harus angka
       'ket'=>'keterangan 1235'
    );

    $json=json_encode($result);
die($json);
}
?>
<script src="jquery.js"></script>
<script>
$(document).ready(function () {
//saya pakai keyup bukan change.. change cocok buat select
    $('#id').keyup(function () {
        var isi = $('#id').val();
//url ganti aja dengan data.php
urlTarget='?p=1'; //"data.php"
        $.ajax({
            url: urlTarget,
            type: "get", //lebih baik post
            data: {
                id: isi
            },
            dataType: "json",
            beforesend: function () {
                $('#t').show();
            },
            success: function (data) {
                $('#nama').html( 'Nama :<input type = "text" name = "nama" value = "'+data.nama+'" />' );
                $('#alamat').html( 'Alamat : <input type = "text" name = "nama" value = "'+ data.alamat+'" >' );
                $('#nomor').html( 'Nomor <input type = "text" name = "nama" value = "'+data.nomor+'" >' );
                $('#ket').html( 'Keterangan<br/><textarea   name = "nama" >'+data.ket+'</textarea> ');

                $('#t').hide()
            }
        });
    });
});
</script>

<input type="text" name="id" id="id" autocomplete='off' placeholder='input disini' x`/>
<span id="t" style="display:none;"></span><br/><br/>
<div id="nama"></div>
<div id="alamat"></div>
<div id="nomor"></div>
<div id="ket"></div>
<!-- kalau gagal cukup hapus komen2 yg ada disini -->