$id= $_GET['id'];
    
	//get today's date
	$pecah			= explode("-",$tgl_pinjam);
	$next_7_hari	= mktime(0,0,0,$pecah[1],$pecah[0]+7,$pecah[2]);
	$hari_next		= date("Y-m-d", $next_7_hari);

	//write a query to update that the book is returned
	$sql = "UPDATE peminjaman SET tgl_kembali='$hari_next' WHERE id_peminjaman='$id'";

	$result = mysqli_query($connection, $sql);

	if($result){
		echo"<script type='text/javascript'>
			onload =function(){
			alert('Data berhasil diperpanjang!');
		document.location='daftar-peminjaman.php';
		}
		</script>";
	}else{
			echo "<script>alert('Data gagal diperpanjang. Silahkan cek kembali.');</script>";
	}