Shortcode to print posts inside a page

<?php
/*
 * Shortcode to print posts inside a page
 * Example: [query category_name="wordpress-code" count=3]
 * Code grabbed from: http://goo.gl/my24k
 */

function queryposts($atts){
    extract( shortcode_atts( array(
    'category_id' => '',
    'category_name' => '',
    'tag' => '',
    'day' => '',
    'month' => '',
    'year' => '',
    'count' => '5',
    'author_id' => '',
    'author_name' => '',
    'order_by' => 'date',
    ), $atts));

    $output = '';

    $query = array();

    // create the query string
    if ($category_id != '') $query[] = 'cat=' .$category_id;
    if ($category_name != '') $query[] = 'category_name=' .$category_name;
    if ($tag != '') $query[] = 'tag=' . $tag;
    if ($day != '') $query[] = 'day=' . $day;
    if ($month != '') $query[] = 'monthnum=' . $month;
    if ($year != '') $query[] = 'year=' . $year;
    if ($count) $query[] = 'posts_per_page=' .$count;
    if ($author_id != '') $query[] = 'author=' . $author_id;
    if ($author_name != '') $query[] = 'author_name=' . $author_name;
    if ($order_by) $query[] = 'orderby=' . $order_by;

    ob_start(); // output to buffer

    // backup the $post variable so it doesn't mess it up if called again
    $backup = $post;

    $posts = new WP_Query(implode('&',$query));

    while ($posts->have_posts()): $posts->the_post();

    // copy here the post layout from your theme's index.php file -- this is just a example ?>
    <h2> <?php the_title(); ?></h2>
    <?php the_content(); ?>

    <?php
    endwhile;

    $post = $backup; // restore the original $post
    wp_reset_query();

    // store the buffer output in the $output variable
    $output = ob_get_contents();
    ob_end_clean();

    return $output;
}

add_shortcode('query', 'queryposts');