WordPressでカテゴリの年ごとのアーカイブを出力する

add_filter( 'widget_archives_args','my_archives');
function my_archives( $content ){
	$content['type'] 	= 'yearly';
	$content['after'] 	= '<span class="year-name">年</span>'; //200Xの後に"年"を表示
	$content['limit'] 	= 15; //n年分を表示、この場合5年
	return $content;
}

<?php

function extend_date_archives_add_rewrite_rules() {
  add_rewrite_rule( 'category/([^/]+)/date/([0-9]{4})/([0-9]{1,2})/([0-9]{1,2})/feed/(feed|rdf|rss|rss2|atom)/?$', 'index.php?category_name=$matches[1]&year=$matches[2]&monthnum=$matches[3]&day=$matches[4]&feed=$matches[4]', 'top' );
	add_rewrite_rule( 'category/([^/]+)/date/([0-9]{4})/([0-9]{1,2})/([0-9]{1,2})/?$', 'index.php?category_name=$matches[1]&year=$matches[2]&monthnum=$matches[3]&day=$matches[4]', 'top' );
	add_rewrite_rule( 'category/([^/]+)/date/([0-9]{4})/([0-9]{1,2})/?$', 'index.php?category_name=$matches[1]&year=$matches[2]&monthnum=$matches[3]', 'top' );
	add_rewrite_rule( 'category/([^/]+)/date/([0-9]{4})/?$', 'index.php?category_name=$matches[1]&year=$matches[2]', 'top' );
	add_rewrite_rule( 'category/([^/]+)/date/([0-9]{4})/page/([0-9]+)/?$', 'index.php?category_name=$matches[1]&year=$matches[2]&paged=$matches[3]', 'top' );//ページネーション対応
}
add_action('wp_loaded', 'extend_date_archives_add_rewrite_rules');


function extend_date_wp_title ($title , $sep, $seplocation) {
	if(is_date()){
		global $wp_query;
		$cat = get_category( $wp_query->query_vars["cat"]);
		if( $seplocation == "right" ){
			$title = $title." ".$cat->name." ".$sep." ";
		}else {
			$title = " ".$sep." ".$cat->name." ".$title;
		}
	}
	return $title;
}
add_filter('wp_title','extend_date_wp_title', 100 ,3 );

function wp_get_category_archive($cat_ID) {
	global $wpdb;
	
	$cat = get_category( $cat_ID );

	//親カテゴリーの場合は、直下に記事がある場合と子カテゴリまで含む場合をORで結ぶ

	if($cat->parent==0){
		$query="
		SELECT YEAR(post_date) AS post_year,count(*) AS num
		FROM $wpdb->posts p, $wpdb->term_relationships tr, $wpdb->term_taxonomy tt, $wpdb->terms t
		WHERE p.ID = tr.object_id
		AND (( tt.parent = $cat_ID ) OR (tt.term_id = $cat_ID ))
		AND t.term_id = $cat_ID
		AND tr.term_taxonomy_id = tt.term_taxonomy_id
		AND p.post_status = 'publish'
		AND p.post_type = 'post'
		GROUP BY post_year
		ORDER BY post_year DESC
		";

	}else{
		$query="
			SELECT YEAR(post_date) AS post_year,count(*) AS num
			FROM $wpdb->posts p, $wpdb->term_relationships tr, $wpdb->term_taxonomy tt, $wpdb->terms t
			WHERE p.ID = tr.object_id
			AND tt.term_id = $cat_ID
			AND t.term_id = $cat_ID
			AND tr.term_taxonomy_id = tt.term_taxonomy_id
			AND p.post_status = 'publish'
			AND p.post_type = 'post'
			GROUP BY post_year
			ORDER BY post_year DESC
		";
	}
	$results = $wpdb->get_results($wpdb->prepare($query));
	?>
	<ul class="cat-archive">
	<?php 
	foreach ($results as $result) :?>
	<li><a href="<?php bloginfo('url'); ?>/category/<?php echo $cat->slug;?>/date/<?php echo $result->post_year; ?>"><?php echo $result->post_year; ?>年<span class="post-count"><?php echo $result->num; ?></span></a></li>
	<?php endforeach; ?>
	</ul>
<?php
}

add_shortcode('cat_archive',function(){
	ob_start();
	if(is_category()){
        $cat_id = get_query_var('cat'); 
	}else if(is_single()){
		$cat = get_the_category();

		if(isset($cat[0])){
			$cat = $cat[0];
			$cat_name = $cat->name;
			$cat_id   = $cat->cat_ID;
		}else{
			return;
		}
	}else{
		return ob_get_clean();
	}

	wp_get_category_archive($cat_id);
	return ob_get_clean();
});

[cat_archive]

if ( get_query_var('year') ) {
    echo get_query_var('year');
}