Pagination on category.php and tag.php not working

Question

i'm using a query-loop on my template pages like this:

<?php
$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
$wp_query = new WP_Query();
$wp_query->query('posts_per_page='.get_option('posts_per_page').'&paged=' . $paged);
global $wp_query;
    query_posts(array_merge($wp_query->query, array(
        'paged'          => get_query_var('paged'),
        'posts_per_page' => 2
    )));
?>
<?php if ($wp_query->have_posts()) : ?>
<?php while ($wp_query->have_posts()) : $wp_query->the_post(); ?>
        <div class="portfolioitem">
    <a href="<?php the_permalink() ?>">
                <?php the_post_thumbnail( 'portfolioteaser' ); ?>
                <div class="mask">
                    <h2><?php the_title(); ?></h2>
                </div>
            </a>
        </div>
         <?php endwhile; ?>
<?php endif; ?> 

the pagination works fine with this except on the category.php or tag.php. The first page is showing correctly but for example if i click on "category/categoryname/page/2" it shows no content anymore an dthe pagination disappears...

i know it must be something wrong with the query loop...

help would be nice! thanks alot, Jochen

Answer 1

If you merely want to modify posts_per_page for tag and category archive index pages, don't use query_posts(); instead, filter the $query via pre_get_posts:

function wpse87489_filter_pre_get_posts( $query ) {
    if ( ( is_category() || is_tag() ) && $query->is_main_query ) {
        $query->set( 'posts_per_page', '2' );
    }
}
add_action( 'pre_get_posts', 'wpse87489_filter_pre_get_posts' );

Answer 2

Please use the following code:

$arg = array (
    'posts_per_page' => get_option('posts_per_page'), 
    'paged' => ( get_query_var('paged') ? get_query_var('paged') : 1 ) 
);
$wp_query = new WP_Query($arg);
if ($wp_query->have_posts()) :
    while ($wp_query->have_posts()) : $wp_query->the_post();
        // do something
    endwhile;
endif;