Besondere Unterseiten-Navigation

function get_counternavi( $show_parent = true, $show_on_parent = true ) {
    global $post;
    
    $show = true;
    
    if( $post->post_parent ) {
        $partentid = $post->post_parent;    
    }
    else {
        if( $show_on_parent == false ) {
            $show = false;
        }
        $partentid = $post->ID;
    }
    
    $pages = get_pages( array( 'child_of' => $partentid, 'sort_column' => 'menu_order', 'sort_order' => 'ASC' ) );
    
    $parentlink = '<a href="'.get_permalink( $partentid ).'" title="'.get_the_title( $partentid).'">'.get_the_title( $partentid).'</a>';
    
    $link_array = array();
    
    if( $show_parent ) {
        array_push( $link_array, $parentlink );
        $counter = 1;
    }
    else {
        $counter = 0;
    }
    
    $current = 0;
    
    foreach( $pages as $p ) {
        $id            = $p->ID;
        $url         = get_permalink( $p->ID );
        $title         = $p->post_title;
        $link        = '<a href="'.$url.'" title="'.$title.'">'.$title.'</a>';
        array_push( $link_array, $link );


        if( $post->ID == $p->ID ) {
            $current = $counter;
        }
        
        $counter ++;
    }
    
    $links = array();
    
    $anzahl = count( $link_array );
    
    if( $current == 0 ) {
        $links['next'] = 'Weiter zu '.$link_array[1];
    }
    elseif( $current == $anzahl - 1 ) {
        $links['prev'] = 'Zurück zu '.$link_array[ $anzahl - 2 ];
    }
    else {
        $links['prev'] = 'Zurück zu '.$link_array[ $current - 1 ];
        $links['next'] = 'Weiter zu '.$link_array[ $current + 1 ];
    }
    
    $output = '<p class="navigation">'.($current + 1).'/'.($anzahl).' | '.implode( ' | ', $links );    
    
    if( $show ) {
        return $output;
    }
    else {
        return '';
    }
}