wordpressのMonthly Archiveで「前の月」「次の月」

global $wpdb, $m, $monthnum, $year, $timedifference, $wp_locale, $posts;

// Let's figure out when we are
if ( !empty($monthnum) && !empty($year) ) {
$thismonth = ''.zeroise(intval($monthnum), 2);
$thisyear = ''.intval($year);
} elseif ( !empty($w) ) {
// We need to get the month from MySQL
$thisyear = ''.intval(substr($m, 0, 4));
$d = (($w - 1) * 7) + 6; //it seems MySQL's weeks disagree with PHP's
$thismonth = $wpdb->get_var("SELECT DATE_FORMAT((DATE_ADD('${thisyear}0101', INTERVAL $d DAY) ), '%m')");
} elseif ( !empty($m) ) {
$calendar = substr($m, 0, 6);
$thisyear = ''.intval(substr($m, 0, 4));
if ( strlen($m) < 6 ) $thismonth = '01'; else $thismonth = ''.zeroise(intval(substr($m, 4, 2)), 2); } else { $thisyear = gmdate('Y', current_time('timestamp')); $thismonth = gmdate('m', current_time('timestamp')); } $unixmonth = mktime(0, 0 , 0, $thismonth, 1, $thisyear); // Get the next and previous month and year with at least one post $previous = $wpdb->get_row("SELECT DISTINCT MONTH(post_date) AS month, YEAR(post_date) AS year
FROM $wpdb->posts
WHERE post_date < '$thisyear-$thismonth-01'
AND post_type = 'post' AND post_status = 'publish'
ORDER BY post_date DESC
LIMIT 1");
$next = $wpdb->get_row("SELECT DISTINCT MONTH(post_date) AS month, YEAR(post_date) AS year
FROM $wpdb->posts
WHERE post_date > '$thisyear-$thismonth-01'
AND MONTH( post_date ) != MONTH( '$thisyear-$thismonth-01' )
AND post_type = 'post' AND post_status = 'publish'
ORDER BY post_date ASC
LIMIT 1");

if ( $previous ) {
echo '<a href="' . get_month_link($previous->year, $previous->month) . '" title="' . sprintf(__('View posts for %1$s %2$s'), $wp_locale->get_month($previous->month),date('Y', mktime(0, 0 , 0, $previous->month, 1, $previous->year))) . '">前の月：' . sprintf(__('%1$s %2$d'), $wp_locale->get_month($previous->month),date('Y', mktime(0, 0 , 0, $previous->month, 1, $previous->year))) . 'の記事を見る</a><br />';
} else {
echo 'これより前の月にはエントリーがありません。<br />';
}

if ( $next ) {
echo '<a href="' . get_month_link($next->year, $next->month) . '" title="' . sprintf(__('View posts for %1$s %2$s'), $wp_locale->get_month($next->month), date('Y', mktime(0, 0 , 0, $next->month, 1, $next->year))) . '">次の月：' . sprintf(__('%1$s %2$d'), $wp_locale->get_month($next->month), date('Y', mktime(0, 0 , 0, $next->month, 1, $next->year))) . 'の記事を見る</a><br />';
} else {
echo 'これより後の月にはエントリーがありません。<br />';
}