检查页面是否有孩子:
class Thumbnail_walker extends Walker_page {
function start_el(&$output, $page, $depth, $args, $current_page) {
if ( $depth )
$indent = str_repeat("\t", $depth);
else
$indent = '';
extract($args, EXTR_SKIP);
$css_class = array('page_item', 'page-item-'.$page->ID);
if ( !empty($current_page) ) {
$_current_page = get_page( $current_page );
_get_post_ancestors($_current_page);
if ( isset($_current_page->ancestors) && in_array($page->ID, (array) $_current_page->ancestors) )
$css_class[] = 'current_page_ancestor';
if ( $page->ID == $current_page )
$css_class[] = 'current_page_item';
elseif ( $_current_page && $page->ID == $_current_page->post_parent )
$css_class[] = 'current_page_parent';
} elseif ( $page->ID == get_option('page_for_posts') ) {
$css_class[] = 'current_page_parent';
}
$css_class = implode( ' ', apply_filters( 'page_css_class', $css_class, $page, $depth, $args, $current_page ) );
$children = get_children( 'post_type=page&numberposts=1&post_parent=' . $page->ID );
if ( empty($children) ) {
$link_contents = $link_before . apply_filters( 'the_title', '' ) . $link_after . get_the_post_thumbnail($page->ID, array(72,72));
}
else {
$link_contents = $link_before . apply_filters( 'the_title', $page->post_title, $page->ID ) . $link_after;
}
$output .= $indent . '<li class="' . $css_class . '"><a href="' . get_permalink($page->ID) . '">' . $link_contents .'</a>';
if ( !empty($show_date) ) {
if ( 'modified' == $show_date )
$time = $page->post_modified;
else
$time = $page->post_date;
$output .= " " . mysql2date($date_format, $time);
}
}
}