Using "UPDATE" in Mysql creates a new record instead of updating the one I just edited

I have a code to be able to edit articles and that when saving them, the database is updated. The HTML code:

<form class="articulos" enctype="multipart/form-data" action="editar.php" method="post">

        <input type="hidden" name="id" value="<?php echo $post['ID'] ?>">
        <h1>Título</h1>
        <input type="text" name="titulo" value="<?php echo $post['titulo'] ?>">

        <h1>Publicado por:</h1>
        <select class="select" name="creador">
            <option name="Egoi" value="Egoi" <?php if ($creador == 'Egoi Cantero') {echo 'selected';} ?>>Egoi Cantero</option>
        </select>

        <h1>Categoria:</h1>
        <select class="select" name="categoria">
            <option name="Articulo" value="Articulo" <?php if ($categoria == 'Articulo') {echo 'selected';} ?>>Articulo</option>
            <option name="Analisis" value="Analisis" <?php if ($categoria == 'Analisis') {echo 'selected';} ?>>Análisis</option>
        </select>

        <h1>Artículo</h1>
        <textarea name="articulo"><?php echo $post['articulo'] ?></textarea>

        <input class="fichero" type="file" name="thumb">

        <input class="enviar" type="submit" name="enviar" value="Guardar cambios">


    </form>

The PHP code, the first thing it does is load the information through the ID.

   <?php

    $id = $_GET['ID'];

    try {
    $conexion = new PDO("mysql:host=localhost;dbname=Blog", 'root', '' );
    } catch (Exception $e) {
    echo "Error: " . $e->getMessage;
    die();
    }

    if (isset($_POST['enviar']) AND $conexion) {

    $creador = isset($_GET['creador']) ? $_GET['creador'] : 'Egoi Cantero';
    $categoria = isset($_GET['categoria']) ? $_GET['categoria'] :    'Articulo';

    $titulo = trim($_POST['titulo']);
    $publicado = $creador;
    $id = trim($_POST['ID']);
    $categoria = $categoria;
    $thumb = $_FILES['thumb']['tmp_name'];
    $thumb_db = $_FILES['thumb']['name'];
    $articulo = $_POST['articulo'];

    $ruta = '../imagenes/articulos/' . $thumb_db;

    $statement = $conexion->prepare("UPDATE art SET
        titulo = :titulo,
        thumb = :thumb,
        publicado_por = :publicado,
        categoria = :categoria,
        articulo = :articulo
    WHERE id = $id");

    $statement->execute(array(
        ':titulo' => $titulo,
        ':thumb' => $thumb_db,
        ':publicado' => $publicado,
        ':categoria' => $categoria,
        ':articulo' => $articulo
    ));

    header('panel_control.php');
    echo "hola";


    } else {

    $statement = $conexion->prepare("SELECT * FROM art WHERE id = $id");
    $statement->execute();
    $posts = $statement->fetchAll();

    $post = $posts[0];
    $creador = $post['publicado_por'];
    $categoria = $post['categoria'];
    }

    require '../views/editar.view.php';

?>

I just did not find the error. Also, do not redirect me to " panel_control.php " or show me "hello" on the screen, I've put it to know if I was entering that part of the code.

Changing the line of code

$id = $_POST['ID'];

By

$id = $_POST['id'];

The header works, that is, it redirects me, although the entry in the database is not updated.