function filter_where_older( $where = \'\' ) {
    $date = get_the_time(\'Y-m-d H:i:s\');
    $where .= " AND post_date < \'$date\'";
    return $where;
}

function filter_where_newer( $where = \'\' ) {
    $date = get_the_time(\'Y-m-d H:i:s\');
    $where .= " AND post_date > \'$date\'";
    return $where;
}

$category = get_the_category();
if(!empty($category)) {

    $cat_id = $category[0]->term_id;

    add_filter( \'posts_where\', \'filter_where_older\' );
    // retrieve older posts from current post
    $query = new WP_Query( "cat=$cat_id&order=ASC&posts_per_page=5" );
    remove_filter( \'posts_where\', \'filter_where_older\' );

    add_filter( \'posts_where\', \'filter_where_newer\' );
    // retrieve newer posts from current post
    $query = new WP_Query( "cat=$cat_id&posts_per_page=5" );
    remove_filter( \'posts_where\', \'filter_where_newer\' );

}