WordPress Loop shortcode for all of today's posts with image

function myLoop($atts, $content = null) {
    extract(shortcode_atts(array(
        "pagination" => 'true',
        "query" => '',
        "category" => '',
    ), $atts));

    global $wp_query,$paged,$post;
    $temp = $wp_query;
    $today = getdate();
    $wp_query = new WP_Query( 'year=' . $today["year"] . '&monthnum=' . $today["mon"] . '&day=' . $today["mday"] );
    if($pagination == 'true'){
        $query .= '&paged='.$paged;
    }
    if(!empty($category)){
        $query .= '&category_name='.$category;
    }
    if(!empty($query)){
        $query .= $query;
    }

    ob_start();
    ?>
    <h2><?php echo $category; ?></h2>
    <ul class="loop">
    <?php while ($wp_query->have_posts()) : $wp_query->the_post(); ?>
        <li><a href="<?php the_permalink() ?>" rel="bookmark"><?php echo the_post_thumbnail('thumbnail'); the_title(); ?></a></li>
    <?php endwhile; ?>
    </ul>
    <?php if(pagination == 'true'){ ?>
    <div class="navigation">
      <div class="alignleft"><?php previous_posts_link('« Previous') ?></div>
      <div class="alignright"><?php next_posts_link('More »') ?></div>
    </div>
    <?php } ?>
    <?php $wp_query = null; $wp_query = $temp;
    $content = ob_get_contents();
    ob_end_clean();
    return $content;
}
add_shortcode("loop", "myLoop");