<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "test";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

if(isset($_REQUEST['id'])){
    $id=intval($_REQUEST['id']);
    $comment=$_REQUEST['comment'];
    $sql = "UPDATE `table1` SET `comment` = '$comment' WHERE `table1`.`id` = $id;";
    $result = $conn->query($sql);
}


$sql = "SELECT * FROM table1";
$result = $conn->query($sql);
?>

<form>

<?php
$row = $result->fetch_assoc();
echo '<input type="hidden" name="id" value="'.$row["id"].'">';
echo '<textarea name="comment" rows="4" cols="50">'.$row["comment"]. "</textarea>";
$conn->close();
?>
<input type="submit"/>
</form>