adding to page and category links

function mag_add_issue_to_link ( $url ) {

return add_query_arg( 'issue' , mag_get_current_issue() , $url );

}

// ensure issue is added to page links, category links and search links
add_filter( 'page_link', 'mag_add_issue_to_link' );
add_filter( 'category_link', 'mag_add_issue_to_link' );