在表单中发送使用PHP定义的值的优势

Question

EDIT: This code isnt for debugging, it is written only as an example and doesnt need completion as the point of it is just seeing the advantages of using a HIDDEN input in a form to retrieve some value. The answers may also be quick and graphic or metaphorical. I dont want a working code, just the advantages of using each methodology. I also fixed an imaginary condition to the while loop and a value for $record_id and placed them so you can understand.

<?php
    if (isset($_POST['delete_action'])) {
        $deletedRow = $_POST['row_to_be_deleted'];
        mysqli_query($connection, "DELETE FROM table_name WHERE record_id = " . $deletedRow);
        //Here is where hidden field value is used
    }

    $someSQL = "SELECT * FROM comments_tbl WHERE postID=$PostRetrievedID";

    while ($someFetch = mysqli_fetch_array($con, $someSQL)) {
        $record_id = $someFetch['comment_ID'];
        $record_content = $someFetch['comment_Content'];
        ?>

        <span>
            <?php echo $record_content; ?>
        </span>
        <form method="post">
            <input type="hidden" name="row_to_be_deleted" value="<?php echo $record_id; ?>"/>
            <input type="submit" name="delete_action" value="Delete comment"/>
        </form>

        <?php
    }
?>

Answer 1

If your question is about why hidden fields even exists, then I have to say that they are used on lots of websites for the exact reason you show in the example.

Lots of times, when you have a form and the user submits it, you need some extra data that the user should not see so that you can manage the data the user submitted. Like in you example, one common use is to atach the ID of the row.