require aksi sebelum script yg tadi....

<?php
session_start();
error_reporting(0);
include "config/koneksi.php";
include "config/library.php";

if (empty($_SESSION[username]) AND empty($_SESSION[password])) {
    header('location:home.php?module=warning');
}
else {

    $module=$_GET[module];
    $act=$_GET[act];

    if ($module=='keranjang' AND $act=='tambah'){

        $sid = $_SESSION[email];

        $sql2 = mysqli_query($con,"SELECT stok FROM produk WHERE id_produk='$_GET[id]'");
        $r=mysqli_fetch_array($sql2);
        $stok=$r[stok];

      if ($stok == 0){
          echo "stok habis";
      }
      else{
        // check if the product is already
        // in cart table for this session
        $sql = mysqli_query($con,"SELECT id_produk FROM orders_temp
                WHERE id_produk='$_GET[id]' AND id_session='$sid'");
        $ketemu=mysqli_num_rows($sql);
        if ($ketemu==0){
            // put the product in cart table
            mysqli_query($con,"INSERT INTO orders_temp (id_produk, jumlah, id_session, tgl_order_temp, jam_order_temp, stok_temp)
                    VALUES ('$_GET[id]', 1, '$sid', '$tgl_sekarang', '$jam_sekarang', '$stok')");
        } else {
            // update product quantity in cart table
            mysqli_query($con,"UPDATE orders_temp
                    SET jumlah = jumlah + 1
                    WHERE id_session ='$sid' AND id_produk='$_GET[id]'");
        }
        deleteAbandonedCart();
        header('Location:home.php?module=keranjangbelanja');
      }
    }

    elseif ($module=='keranjang' AND $act=='hapus'){
        mysqli_query($con,"DELETE FROM orders_temp WHERE id_orders_temp='$_GET[id]'");
        header('Location:home.php?module=keranjangbelanja');
    }

elseif ($module=='keranjang' AND $act=='update'){
  $id       = $_POST[id];
  $jml_data = count($id);
  $jumlah   = $_POST[jml]; // quantity
  for ($i=1; $i <= $jml_data; $i++){
    $sql2 = mysqli_query($con,"SELECT stok_temp FROM orders_temp    WHERE id_orders_temp='".$id[$i]."'");
    while($r=mysqli_fetch_array($sql2)){
    if ($jumlah[$i] > $r[stok_temp]){
        echo "<script>window.alert('Jumlah yang dibeli melebihi stok yang ada');
        window.location=('home.php?module=keranjangbelanja')</script>";
    }
    elseif($jumlah[$i] == 0){
        echo "<script>window.alert('Anda tidak boleh menginputkan angka 0 atau mengkosongkannya!');
        window.location=('home.php?module=keranjangbelanja')</script>";
    }
    else{
      mysqli_query($con,"UPDATE orders_temp SET jumlah = '".$jumlah[$i]."'
                                      WHERE id_orders_temp = '".$id[$i]."'");
      header('Location:home.php?module=keranjangbelanja');
    }
  }
  }
}
}

/*
    Delete all cart entries older than one day
*/
function deleteAbandonedCart(){
    $kemarin = date('Y-m-d', mktime(0,0,0, date('m'), date('d') - 1, date('Y')));
    mysqli_query($con,"DELETE FROM orders_temp
            WHERE tgl_order_temp < '$kemarin'");
}
?>