このすぐ下の回答に記載されているpost_galleryフィルターを見逃しました。関数全体をコピーするのではなく、そのフィルターの使用を検討する必要があります。
このコードをテンプレートのfunctions.phpに追加し、関数内のHTMLを変更します。この関数は、WP35のデフォルトのギャラリーショートコード関数のコピーです。Codexによると、各ショートコードに割り当てることができる関数は1つだけです。そのため、関数はWordPressのデフォルトの関数をオーバーライドします。
add_shortcode('gallery', 'my_gallery_shortcode');
function my_gallery_shortcode($attr) {
$post = get_post();
static $instance = 0;
$instance++;
if ( ! empty( $attr['ids'] ) ) {
// 'ids' is explicitly ordered, unless you specify otherwise.
if ( empty( $attr['orderby'] ) )
$attr['orderby'] = 'post__in';
$attr['include'] = $attr['ids'];
}
// Allow plugins/themes to override the default gallery template.
$output = apply_filters('post_gallery', '', $attr);
if ( $output != '' )
return $output;
// We're trusting author input, so let's at least make sure it looks like a valid orderby statement
if ( isset( $attr['orderby'] ) ) {
$attr['orderby'] = sanitize_sql_orderby( $attr['orderby'] );
if ( !$attr['orderby'] )
unset( $attr['orderby'] );
}
extract(shortcode_atts(array(
'order' => 'ASC',
'orderby' => 'menu_order ID',
'id' => $post->ID,
'itemtag' => 'dl',
'icontag' => 'dt',
'captiontag' => 'dd',
'columns' => 3,
'size' => 'thumbnail',
'include' => '',
'exclude' => ''
), $attr));
$id = intval($id);
if ( 'RAND' == $order )
$orderby = 'none';
if ( !empty($include) ) {
$_attachments = get_posts( array('include' => $include, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby) );
$attachments = array();
foreach ( $_attachments as $key => $val ) {
$attachments[$val->ID] = $_attachments[$key];
}
} elseif ( !empty($exclude) ) {
$attachments = get_children( array('post_parent' => $id, 'exclude' => $exclude, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby) );
} else {
$attachments = get_children( array('post_parent' => $id, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby) );
}
if ( empty($attachments) )
return '';
if ( is_feed() ) {
$output = "\n";
foreach ( $attachments as $att_id => $attachment )
$output .= wp_get_attachment_link($att_id, $size, true) . "\n";
return $output;
}
$itemtag = tag_escape($itemtag);
$captiontag = tag_escape($captiontag);
$icontag = tag_escape($icontag);
$valid_tags = wp_kses_allowed_html( 'post' );
if ( ! isset( $valid_tags[ $itemtag ] ) )
$itemtag = 'dl';
if ( ! isset( $valid_tags[ $captiontag ] ) )
$captiontag = 'dd';
if ( ! isset( $valid_tags[ $icontag ] ) )
$icontag = 'dt';
$columns = intval($columns);
$itemwidth = $columns > 0 ? floor(100/$columns) : 100;
$float = is_rtl() ? 'right' : 'left';
$selector = "gallery-{$instance}";
$gallery_style = $gallery_div = '';
if ( apply_filters( 'use_default_gallery_style', true ) )
$gallery_style = "
<style type='text/css'>
#{$selector} {
margin: auto;
}
#{$selector} .gallery-item {
float: {$float};
margin-top: 10px;
text-align: center;
width: {$itemwidth}%;
}
#{$selector} img {
border: 2px solid #cfcfcf;
}
#{$selector} .gallery-caption {
margin-left: 0;
}
</style>
<!-- see gallery_shortcode() in wp-includes/media.php -->";
$size_class = sanitize_html_class( $size );
$gallery_div = "<div id='$selector' class='gallery galleryid-{$id} gallery-columns-{$columns} gallery-size-{$size_class}'>";
$output = apply_filters( 'gallery_style', $gallery_style . "\n\t\t" . $gallery_div );
$i = 0;
foreach ( $attachments as $id => $attachment ) {
$link = isset($attr['link']) && 'file' == $attr['link'] ? wp_get_attachment_link($id, $size, false, false) : wp_get_attachment_link($id, $size, true, false);
$output .= "<{$itemtag} class='gallery-item'>";
$output .= "
<{$icontag} class='gallery-icon'>
$link
</{$icontag}>";
if ( $captiontag && trim($attachment->post_excerpt) ) {
$output .= "
<{$captiontag} class='wp-caption-text gallery-caption'>
" . wptexturize($attachment->post_excerpt) . "
</{$captiontag}>";
}
$output .= "</{$itemtag}>";
if ( $columns > 0 && ++$i % $columns == 0 )
$output .= '<br style="clear: both" />';
}
$output .= "
<br style='clear: both;' />
</div>\n";
return $output;
}