PHP - Undefined index : id - the value is not retrieved - php

Question

Yes, I know there is a lot of 'Undefined index' questions floating around here and i have been looking through them before asking this question. I copied the codes from those questions to try and test it out but it still doesn't work for my own project. Also, I'm still a beginner in PHP.
So here is my problem. I wanted to try coding a simple edit form after I have finished coding the delete and view form.
This is my code
<?php
require("config.php");
$id = $_GET['id'];
echo "id: ".$id;
$sql = "SELECT * FROM contracts WHERE id= '$id'";
$result = $con->query($sql);
$row = $result->fetch_assoc()
?>
<form action="editform.php" method="GET">
ID:
<?php echo $id; ?><br>
Contract Title<br>
<input type="text" name="contract_title" value="<?php echo $row['contract_title']; ?>" /><br>
<input type="submit" name = "edit "value="Update" />
</form>
?php
if(isset($_POST['edit']) ){
$id = $_GET['id'];
$upd= "UPDATE `contracts` SET
`contract_title`='".$_POST['contract_title']."',
WHERE `id`='".$_POST['id']."";
if($do_upd = $con->query($upd))
{
echo "Update Success";
}
else
{
echo "Update Fail";
}
}
?>
This is the before the error.
This is the error I received.
In line 3, the id is not retrieved after I clicked the button update.
It didn't retrieved the values.
What mistakes did I do in the coding and how do I fix it? Thanks in advance.

Answer 1

Right below:
<form action="editform.php" method="GET">
Add:
<input type="hidden" name="id" value="<?php echo $id; ?>" />
Update:
Fixed other errors in your code:
<?php
require("config.php");
$id = $_GET['id'];
echo "id: ".$id;
$sql = "SELECT * FROM contracts WHERE id= '$id'";
$result = $con->query($sql);
$row = $result->fetch_assoc()
?>
<form action="editform.php" method="GET">
ID: <?php echo $id; ?><br>
Contract Title<br>
<input type="hidden" name="id" value="<?php echo $id; ?>" />
<input type="text" name="contract_title" value="<?php echo $row['contract_title']; ?>" /><br>
<input type="submit" name="edit" value="Update" />
</form>
<?php
if(isset($_GET['edit']) ){
// needs escaping!~~~
$upd= "UPDATE `contracts` SET `contract_title` = '".$_GET['contract_title']."' WHERE `id` = '".$id;
if($do_upd = $con->query($upd)) {
echo "Update Success";
} else {
echo "Update Fail";
}
}
Please consider escaping your database input to prevent SQL injection

Answer 2

<?php
require("config.php");
$id = $_GET['id'];
echo "id: ".$id;
$sql = "SELECT * FROM contracts WHERE id= '$id'";
$result = $con->query($sql);
$row = $result->fetch_assoc()
if ($result->num_rows > 0) {
// output data of each row
while($row = $result->fetch_assoc()) {
$contract_title = $row['contract_title'];
}
} else {
echo "0 results";
}
if(isset($_POST['edit']) ){
$upd = "UPDATE contracts SET contract_title='$contract_title' WHERE id='$id'";
if($do_upd = $con->query($upd))
{
echo "Update Success";
}
else
{
echo "Update Fail";
}
}
?>
<form action="" method="POST">
ID:
<?php echo $id; ?><br>
Contract Title<br>
<input type="text" name="contract_title" value="<?php echo $row['contract_title']; ?>" /><br>
<input type="submit" name = "edit" value="Update" />
</form>