如何使用PHP和MySQL更新数据库中项目的单个字段

<?php 
            if (isset($_POST['notes'])) {                                   
                $input = $_POST['notes'];
                $id = $row['id'];

            $sql = "UPDATE tasks SET notes ='$input' WHERE id = ($id)";  
            if ($conn->query($sql) === TRUE) {
                echo "New record created successfully";
              } else {
                echo "Error: " . $sql . "<br>" . $conn->error;
              } } ?>

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