update php&mysql : undefined index - php

Question

I'm now making reservation system, and something is wrong with updating data. I made table updateMy_ReservationView.php like this.
this is an image of SelectMy_ReservationView.php I have an error with insert more codes because of this editor's error message.
<?php
include "connection.php";
$id=$_GET['reservation_id'];
$sql = "select reservation.*, customer.*, car_type.*, datediff(return_time,
rent) as total_day, (datediff(return_time, rent) * price ) AS total_price
FROM
reservation, customer, car_type
WHERE reservation.car_type_id=car_type.car_type_id AND
reservation.customer_id=customer.customer_id and reservation_id='$id' order
by reservation_id ";
$result = mysqli_query($conn, $sql);
$row = mysqli_fetch_assoc($result);
$sql_car = "SELECT car_type.* from car_type";
$result_car = mysqli_query($conn, $sql_car);
?>
<h3><b>Update Reservation</b></h3><br>
<form method = "post" action = "?page=updateMy_ReservationDo">
<table class="table table-striped table-sm"
style="width:500px; height:200px;">
<tr>
<td>Customer Name</td>
<td>
<?php echo" $row[customer_name]";?>
<input type = "hidden" name="reservation_id" value="
<?php echo"$row[reservation_id]";?>">
</td>
</tr>
<tr>
<td>Old car type</td>
<td>
<?php echo" $row[car_type]";?>
</td>
</tr>
<tr>
<td>New Car Type (Price USD)</td>
<td>
<select name = "car_type">
<?php
while($row_car = mysqli_fetch_assoc($result_car)) {
?>
<option value="<?php echo"$row_car[car_type_id]";?>">
<?php echo"$row_car[car_type] ($row_car[price])";?></option>
<?php
}
?>
</select>
</td>
</tr>
<tr>
<td>Old Rent</td>
<td><?php echo "$row[rent]"; ?></td>
</tr>
<tr>
<td>Rent</td>
<td><input type="text" name="rent" id="rent"
maxlength="25" size="25"/>
<img src="images_date/cal.gif" alt=""
onclick="javascript:NewCssCal('rent','yyyyMMdd','arrow',false,'24',false)"
style="cursor:pointer"/></td>
</tr>
<tr>
<td>Old Return</td>
<td><?php echo "$row[return_time]"; ?></td>
</tr>
<tr>
<td>Return</td>
<td><input type="text" name="return_time"
id="return_time" maxlength="25" size="25"/>
<img src="images_date/cal.gif" alt=""
onclick="javascript:NewCssCal('return_time','yyyyMMdd'
'arrow',false,'24',false)" style="cursor:pointer"/></td>
</tr>
<tr>
<td>Old Pickup Station</td>
<td><?php echo "$row[car_station]"; ?></td>
</tr>
<tr>
<td>Pickup Station</td>
<td>
<select name = "car_station">
<option value="Yeouido">Yeouido</option>
<option value="Shinchon">Shinchon</option>
<option value="Jongro">Jongro</option>
<option value="Seoul Station">Seoul
Station</option>
<option value="Gangnam">Gangnam</option>
<option value="Geondae">Geondae</option>
</select></td>
</tr>
<tr>
<td> </td>
<td><input type="reset" value="Reset"> <input name = "add" type = "submit" value = "Update Reservation">
</td>
</tr>
</table>
And I made updating function file updateMy_ReservationDo.php like below.
include "connection.php";
$reservation_id=$_POST['reservation_id'];
$car_type=$_POST['car_type_id'];
$rent=$_POST['rent'];
$return_time=$_POST['return_time'];
$car_station=$_POST['car_station'];
$sql = "update reservation set car_type='$car_type_id',rent='$rent',
return_time='$return_time' and car_station='$car_station' where
reservation_id=$reservation_id ";
if (mysqli_query($conn, $sql)) {
echo "Reservation is updated successfully<br>";
echo "<p><p><a href=?page=selectMy_reservationView><button type=button>Show
all reservation</button></a>";
} else {
echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}
mysqli_close($conn);
?>
Then Error message like this happen:
Notice: Undefined index: car_type_id in C:\xampp\htdocs\rentcar\updateMy_ReservationDo.php on line 5
Notice: Undefined variable: car_type_id in C:\xampp\htdocs\rentcar\updateMy_ReservationDo.php on line 10
Error: update reservation set car_type='',rent='2018-05-31', return_time='2018-06-01' and car_station='Shinchon' where reservation_id=17
Unknown column 'car_type' in 'field list'
What should I modify?

Answer 1

Use isset like following :
$reservation_id = isset($_POST['reservation_id']) ? $_POST['reservation_id'] : '';
$car_type = isset($_POST['car_type_id']) ? $_POST['car_type_id'] : '';
$rent = isset($_POST['rent']) ? $_POST['rent'] : '';
$return_time = isset($_POST['return_time']) ? $_POST['return_time'] : '';
$car_station = isset($_POST['car_station']) ? $_POST['car_station'] : '';
and your defined variable is $car_type but you used in your sql query $car_type_id
use :
$car_type
and make sure car_type field exists in your table

Answer 2

Change the name of car_type to car_type_id.The error is due to you are sending car_type and accessing car_type_id in updateMy_ReservationDo.php.
<?php
include "connection.php";
$id=$_GET['reservation_id'];
$sql = "select reservation.*, customer.*, car_type.*, datediff(return_time,
rent) as total_day, (datediff(return_time, rent) * price ) AS total_price
FROM
reservation, customer, car_type
WHERE reservation.car_type_id=car_type.car_type_id AND
reservation.customer_id=customer.customer_id and reservation_id='$id' order
by reservation_id ";
$result = mysqli_query($conn, $sql);
$row = mysqli_fetch_assoc($result);
$sql_car = "SELECT car_type.* from car_type";
$result_car = mysqli_query($conn, $sql_car);
?>
<h3><b>Update Reservation</b></h3><br>
<form method = "post" action = "?page=updateMy_ReservationDo">
<table class="table table-striped table-sm"
style="width:500px; height:200px;">
<tr>
<td>Customer Name</td>
<td>
<?php echo" $row[customer_name]";?>
<input type = "hidden" name="reservation_id" value="
<?php echo"$row[reservation_id]";?>">
</td>
</tr>
<tr>
<td>Old car type</td>
<td>
<?php echo" $row[car_type]";?>
</td>
</tr>
<tr>
<td>New Car Type (Price USD)</td>
<td>
<select name = "car_type_id">
<?php
while($row_car = mysqli_fetch_assoc($result_car)) {
?>
<option value="<?php echo"$row_car[car_type_id]";?>">
<?php echo"$row_car[car_type] ($row_car[price])";?></option>
<?php
}
?>
</select>
</td>
</tr>
<tr>
<td>Old Rent</td>
<td><?php echo "$row[rent]"; ?></td>
</tr>
<tr>
<td>Rent</td>
<td><input type="text" name="rent" id="rent"
maxlength="25" size="25"/>
<img src="images_date/cal.gif" alt=""
onclick="javascript:NewCssCal('rent','yyyyMMdd','arrow',false,'24',false)"
style="cursor:pointer"/></td>
</tr>
<tr>
<td>Old Return</td>
<td><?php echo "$row[return_time]"; ?></td>
</tr>
<tr>
<td>Return</td>
<td><input type="text" name="return_time"
id="return_time" maxlength="25" size="25"/>
<img src="images_date/cal.gif" alt=""
onclick="javascript:NewCssCal('return_time','yyyyMMdd'
'arrow',false,'24',false)" style="cursor:pointer"/></td>
</tr>
<tr>
<td>Old Pickup Station</td>
<td><?php echo "$row[car_station]"; ?></td>
</tr>
<tr>
<td>Pickup Station</td>
<td>
<select name = "car_station">
<option value="Yeouido">Yeouido</option>
<option value="Shinchon">Shinchon</option>
<option value="Jongro">Jongro</option>
<option value="Seoul Station">Seoul
Station</option>
<option value="Gangnam">Gangnam</option>
<option value="Geondae">Geondae</option>
</select></td>
</tr>
<tr>
<td> </td>
<td><input type="reset" value="Reset"> <input name = "add" type = "submit" value = "Update Reservation">
</td>
</tr>
</table>