Hallo, Pak Ellyx. Saya mohon bantuannya.
Saya punya form dinamis untuk transaksi pembelian, yang jumlah form item bisa ditambah sesuai kebutuhan (dinamis)dan pada saat submit, data masuk ke beberapa table.

table pembelian (header) terdiri dari :
kode_beli (primary key), nota_beli, suplier_id, pegawai_id, tanggal_beli, total_beli, keterangan_beli

table detail_pembelian (item) terdiri dari :
id_beli, kode_beli, produk_id, jumlah_beli, harga_beli, total_beli

Setelah di submit, stok barang di table produk akan bertambah sesuai dengan jumlah beli yang di input di form.

Saya sudah mencoba, tapi eror. Mohon bantuannya pak.
saya membuatnya dengan bootstrap, jquery dan ajax.

	<link href="asset/datetimepicker/bootstrap-datetimepicker.min.css" rel="stylesheet">
	<link href="asset/css/bootstrap.min.css" rel="stylesheet">
	<link href="asset/js/jqueryui/jquery-ui.min.css" rel="stylesheet">
	<link href="asset/js/autocomplete/autocomplete-0.3.0.css" rel="stylesheet">
	
	<script type="text/javascript" src="asset/js/jquery-1.11.0.js"></script>
	<script type="text/javascript" src="asset/js/jquery.min.js"></script>
	<script type="text/javascript" src="asset/js/jqueryui/jquery-ui.min.js"></script>
	<script type="text/javascript" src="asset/js/autocomplete/autocomplete-0.3.0.js"></script>
	<script type="text/javascript" src="asset/datetimepicker/bootstrap-datetimepicker.js" charset="UTF-8"></script>
	<script type="text/javascript" src="asset/datetimepicker/bootstrap-datetimepicker.id.js" charset="UTF-8"></script>
	<?php
	$sql=mysql_query("SELECT kode_beli from pembelian order by kode_beli DESC LIMIT 0,1");
	$data=mysql_fetch_array($sql);
	$kodeawal=substr($data['kode_beli'],3,5)+1;
		if($kodeawal<10){
			$kode='BLJ0000'.$kodeawal;
			}
			elseif($kodeawal > 9 && $kodeawal <=99){
				$kode='BLJ000'.$kodeawal;
			}else{
				$kode='BLJ000'.$kodeawal;
			}
	?>

	<?php if($_SERVER['REQUEST_METHOD'] != 'POST'){ ?>
	<div class="container">		
		<div class="row">
			<div class="col-lg-12">
				<form class="form-horizontal" action="" method="POST">				
					<div class="form-group">
						<label for="tanggal_beli" class="col-lg-2 control-label"><strong>Tanggal Beli : </strong></label>
						<div class="col-lg-2">
							<input type="date" class="form-control" id="tanggal_beli" placeholder="Tanggal ..">
						</div>
						
						<label for="total_beli" class="col-lg-2 col-lg-offset-3 control-label"><strong>Total Beli : </strong></label>
						<div class="col-lg-3">
							<div class="input-group"><span class="input-group-addon">Rp</span><input type="text" class="form-control" id="total_beli" name='total_beli' placeholder="Total pembelian .." readonly></div>
						</div>
					</div>
								
					<div class="form-group">
						<label for="kode_beli" class="col-lg-2 control-label"><strong>Kode : </strong></label>
						<div class="col-lg-2">
							<input type="text" maxlength="8" class="form-control uneditable-input" id="kode_beli" name="kode_beli" value="<?php echo $kode;?>"readonly="true" >
						</div>
								
						<label for="nota" class="col-lg-1 control-label"><strong>Nota Beli : </strong></label>
						<div class="col-lg-2">
							<input type="text" maxlength="50" class="form-control" id="nota" name="nota" placeholder="Nota beli ...">
						</div>
									
						<label for="suplier_id" class="col-lg-1 control-label"><strong>Suplier : </strong></label>
						<div class="col-lg-4">
							<select class="form-control" id="suplier_id" name="suplier_id">
								<option value="">Pilih Suplier</option>
								<?php 
								$query = mysql_query("SELECT * FROM suplier");
								while($row = mysql_fetch_array($query)){
									echo '<option value="'.$row['id_suplier'].'">'.$row['nama_suplier'].'</option>';
								} ?>
							</select>
						</div>
					</div>
					
					<div class="form-group">
						<label for="keterangan" class="col-lg-2 col-lg-offset-3 control-label"><strong>Keterangan : </strong></label>
						<div class="col-lg-7">
							<textarea  maxlength="300" rows="2" class="form-control" id="keterangan" name="keterangan" placeholder="Keterangan ..."></textarea>
						</div>
					</div>					
					
					<div class="table-responsive">
					  	<table class="table table-bordered">
							<tr>
							    <th width="2%"><input id="check_all" class="formcontrol" type="checkbox"/></th>
							    <th width="50px">No</th>
								<th width="300px">Nama Produk</th>
							    <th width="150px">Kode Produk</th>
							    <th width="100px">Jumlah Beli</th>
							    <th width="100px">Harga Beli</th>
							    <th width="100px">Total Beli</th>
							</tr>
							<tr>
						    	<td><input type='checkbox' class='case'/></td>
								<td><span id='snum'>1.</span></td>
						   	 	<td><input class="form-control autocomplete_txt" data-type="productNama" type='text' id='namaproduk_1' name='namaproduk[]' autocomplete="off"/></td>
						    	<td><input class="form-control autocomplete_txt" data-type="productKode" type='text' id='kodeproduk_1' name='kodeproduk[]' autocomplete="off" readonly/></td>
						    	<td><input class="form-control changesNo" type='text' id='jumlahbeli_1' name='jumlahbeli[]' autocomplete="off" onkeypress="return IsNumeric(event);" ondrop="return false;" onpaste="return false;"/></td>
						    	<td><div class="input-group"><span class="input-group-addon">Rp</span><input class="form-control changesNo" type='text' id='hargabeli_1' name='hargabeli[]' autocomplete="off" onkeypress="return IsNumeric(event);" ondrop="return false;" onpaste="return false;"/> </div></td>
								<td><div class="input-group"><span class="input-group-addon">Rp</span><input class="form-control totalLinePrice" type='text' id='totalbeli_1' name='totalbeli[]' autocomplete="off" onkeypress="return IsNumeric(event);" ondrop="return false;" onpaste="return false;" readonly/> </div></td>
						  	</tr>
					  	</table>
					</div>	
					<div class="row">
						<div class="col-lg-12">
								<button type="button" class='btn btn-danger delete'><span class="glyphicon glyphicon-trash"> Delete</span></button>
								<button type="button" class='btn btn-success addmore'><span class="glyphicon glyphicon-plus">  Tambah</span></button>
								<input class='btn btn-info' type="submit" value="Simpan" name="simpan" />
						</div>
					</div>
				</form>
					
		
					
					<?php
					} else
						 {
						//simpan ke tabel 'Pembelian'
						$insert_topembelian = "INSERT INTO pembelian VALUES('".$_POST['kode_beli']."', '".$_POST['nota']."', ".$_POST['suplier_id'].", ".$_POST['tanggal_beli'].", ".$_POST['total_beli'].", '".$_POST['keterangan']."')";
						//echo $insert_topembelian;exit;
						mysql_query($insert_topembelian);
						
						//menyimpan data ke tabel 'Detail Pembelian'
						foreach($_POST['kodeproduk'] as $produk_id => $value_kodeproduk){
							foreach($_POST['namaproduk'] as $produk_nm => $value_namaproduk){
								foreach($_POST['jumlahbeli'] as $produk_ttl => $value_jumlahbeli){
									foreach($_POST['hargabeli'] as $produk_price => $value_hargabeli){
										$query_getdetailproduk=mysql_query("SELECT * FROM produk WHERE kode_produk = '$value_kodeproduk'");
										$stk_produk = array(); 
										$id_produk = array();
										$x=0;
										while (($row = mysql_fetch_array($query_getdetailproduk, MYSQL_ASSOC)) !== false)
										{
											$rslt[$x] = $row['stok_produk'];
											$id_produk[$x] = $row['id_produk'];
										}	
										$query="INSERT INTO detail_pembelian (kode_beli, produk_id, jlh_beli, harga_beli, total_beli) 
												VALUES ('$_POST[kode_beli]', $id_produk[0] , $value_jumlahbeli, $value_hargabeli, $_POST[total_beli])";												
															//echo $query;exit;
										if (mysql_query($query)){
										//echo $query;exit;
										$updateproduk = "UPDATE produk SET stok_produk = $rslt[$x] + $value_jumlahbeli WHERE kode_produk = '$value_kodeproduk'";
										mysql_query($updateproduk);
											header('Location: dashboard.php?p=produk');
												}else{
													writeMsg('tambahproduk.gagal');
										}	
									}
								}
							}
						}	
					}

					?>
			</div>
		</div>
	</div>
	<script src="asset/js/autocompletepembelian.js"></script>