Edited all entries in database [php] - php

Question

I have a problem in editing data in my database. I only want to edit one entry but after I clicked edit, it shows that all the data in my database were edited.
eventlist.php
<?php
$con=mysqli_connect("localhost","root","root","chess");
$result = mysqli_query($con,"select * from events");
//echo "<a href='dashboard.php'>Home</a><br>";
echo "<table border=1 id='hor-minimalist-a' width='100%'>";
echo "<tr align='center'><td><b>Date</b></td><td><b>Event</b></td><td><b>Special Note</b></td><td colspan='2'>Options</td></tr>";
$a=0;
while($row = mysqli_fetch_array($result))
{
if($a%2==0){
echo "<tr bgcolor='#b2d5ff' width='100'>"."<td>" . $row['date'] . "</td> <td>" . $row['event'] . "</td> <td>" . $row['note'] . "</td>"
. "</td><td><a href='editevent.php?id=" . $row['id'] . "'>Edit</a></td><td><a href='deleteevent.php?id=" . $row['id'] . "'>Delete</a></td></tr>";
}
else{
echo "<tr>"."<td>" . $row['date'] . "</td> <td>" . $row['event'] . "</td> <td>" . $row['note'] . "</td>"
. "</td><td><a href='editevent.php?id=" . $row['id'] . "'>Edit</a></td><td><a href='deleteevent.php?id=" . $row['id'] . "'>Delete</a></td></tr>";
}
$a++;
}
echo '</table>';
echo "<center><a href='addevent.php'><button type='submit' class='button'>Add New</button></a></center>";
?>
editevent.php
<?php
while($row = mysqli_fetch_array($result))
{
echo "ID: <input type='text' name='id' value='$row[id]'><br/>";
echo "Date: <input type='text' name='date' value='$row[date]'><br/>";
echo "Event: <textarea type='text' name='event'>".$row['event']."</textarea><br/>";
echo "Note: <input type='text' name='note' value='$row[note]'><br/>";
}
?>
updateevent.php
<?php
$id = $_POST['id'];
$date = $_POST['date'];
$event = $_POST['event'];
$note = $_POST['note'];
$con = mysqli_connect("localhost","root","root","chess");
mysqli_query($con,"update events set date='$date', event='$event', note='$note' where id = id");
header('location: eventlist.php');
?>

Answer 1

"update events set date='$date', event='$event', note='$note' where id = id"
where id = id is true for all rows, so all rows get updated. You probably ment to write where id = $id.
Also note that your query is open to SQL injection. Use prepared statements instead.