Undefined Variable Warning in PHP - php

Question

So I've been doing this school project and need to make it so I can edit whatever is in the table. Whenever i click on "Edit" it redirects me correctly but in the form it says there is an undefined variable eventhough that variable is used pretty much everywhere.
Here is some code of the table:
<table style='margin-left:auto ; margin-right:auto;'>
<tr>
<th>#</th>
<th>Name</th>
<th>Zeit</th>
<th>Datum</th>
<th>Titel</th>
<th>Inhalt</th>
<th>Ort</th>
</tr>
<?php
if($stmt=$db->prepare("SELECT * FROM terminkalender")) {
$stmt->execute();
$stmt->store_result();
$zeilen = $stmt->num_rows();
$stmt->close();
}else {
$zeilen = 0;
}
if($zeilen > 0) {
//nur wenn Einträge, dann ausgeben
if($stmt = $db->prepare("SELECT * FROM terminkalender ORDER BY zeit,datum DESC")) {
$stmt->execute();
$stmt->bind_result($id,$name,$zeit,$datum,$ort,$titel,$inhalt);
$stmt->store_result();
//Ausgabe starten
while($stmt->fetch()){
echo "<tr>";
?>
<td><?php echo $id ;?></td>
<td><?php echo htmlspecialchars($name) ;?></td>
<td><?php echo htmlspecialchars($datum) ;?></td>
<td><?php echo htmlspecialchars($zeit) ;?></td>
<td><?php echo htmlspecialchars($ort) ;?></td>
<td><?php echo htmlspecialchars($titel) ;?></td>
<td><?php echo htmlspecialchars($inhalt); ?></td>
<td><a href='edit.php?id=<?php echo $id;?>'>Edit</a></td>
<td><a href='delete.php?id=<?php echo $id;?>'>Delete</a></td>
<?php
echo "</tr>" ;
}
}
}
?>
</table>
and here for the edit.php file:
<?php
include("./config/connect.inc.php");
$id = $_GET['id']; // get id through get string
$result=mysqli_query($db,"SELECT * FROM terminkalender WHERE id=$id");
if(isset($_POST['update'])) {
$name=$_POST['name'];
$datum=$_POST['datum'];
$zeit=$_POST['zeit'];
$ort=$_POST['ort'];
$titel=$_POST['titel'];
$inhalt=$_POST['inhalt'];
$result = "UPDATE terminkalender
SET name='$name',
datum='$datum',
zeit='$zeit',
ort='$ort',
titel='$titel',
inhalt='$inhalt'
WHERE id=$id";
header("location: ausgabe.php");
}
?>
<form name="form" method="POST" action="edit.php">
<input type="text" name="name" value="<?php echo $name; ?>" Required>
<input type="date" name="datum" value="<?php echo $datum; ?>" Required>
<input type="time" name="zeit" value="<?php echo $zeit; ?>" Required>
<input type="text" name="ort" value="<?php echo $ort; ?>" Required>
<input type="text" name="titel" value="<?php echo $titel; ?>" Required>
<input type="text" name="inhalt" value="<?php echo $inhalt; ?>" Required>
<input type="hidden" name="id" value="<?php echo $_GET['id']; ?>">
<input type="submit" name="update" value="Update">
</form>
Ẁould be really awesome if anyone could help. Thanks is advance!

Answer 1

Maybe you can try using isset function of php to check if that variable contains a value or not for more details check:-https://www.stechies.com/notice-undefined-variable-in-php/