記事投稿日を西暦から和暦に変更するプラグイン

先週やった内容を、試しにWordPressプラグインでやってみました。
以下、ネットで情報を漁りながら、自分が作った方法です。

１．wp-content/plugin/wareki というフォルダを作成し、その中に wareki.php を作成する。
２．wareki.php 内のコードは以下のようにして、保存。

<?php
/*
Plugin Name: wareki
Plugin URI: http://www.example.com/plugin
Description: テスト用に作った、西暦を和暦に変更するプラグイン
Author: fukapu
Version: 0.1
Author URI: http://wordpress.nakweb.com
*/

if ( ! function_exists( 'twentytwelve_entry_meta' ) ) :
/**
 * Prints HTML with meta information for current post: categories, tags, permalink, author, and date.
 *
 * Create your own twentytwelve_entry_meta() to override in a child theme.
 *
 * @since Twenty Twelve 1.0
 */
function twentytwelve_entry_meta() {
    // Translators: used between list items, there is a space after the comma.
    $categories_list = get_the_category_list( __( ', ', 'twentytwelve' ) );

    // Translators: used between list items, there is a space after the comma.
    $tag_list = get_the_tag_list( '', __( ', ', 'twentytwelve' ) );

    // 日付を取得し、和暦にする処理
    $ymd = get_the_date('Y/n/j');
    $wareki = wareki($ymd);
    $date = $wareki;
/*
    $date = sprintf( '<a href="%1$s" title="%2$s" rel="bookmark"><time class="entry-date" datetime="%3$s">%4$s</time></a>',
        esc_url( get_permalink() ),
        esc_attr( get_the_time() ),
        esc_attr( get_the_date( 'c' ) ),
        esc_html( get_the_date() )
    );
*/
    $author = sprintf( '<span class="author vcard"><a class="url fn n" href="%1$s" title="%2$s" rel="author">%3$s</a></span>',
        esc_url( get_author_posts_url( get_the_author_meta( 'ID' ) ) ),
        esc_attr( sprintf( __( 'View all posts by %s', 'twentytwelve' ), get_the_author() ) ),
        get_the_author()
    );

    // Translators: 1 is category, 2 is tag, 3 is the date and 4 is the author's name.
    if ( $tag_list ) {
        $utility_text = __( 'This entry was posted in %1$s and tagged %2$s on %3$s<span class="by-author"> by %4$s</span>.', 'twentytwelve' );
    } elseif ( $categories_list ) {
        $utility_text = __( 'This entry was posted in %1$s on %3$s<span class="by-author"> by %4$s</span>.', 'twentytwelve' );
    } else {
        $utility_text = __( 'This entry was posted on %3$s<span class="by-author"> by %4$s</span>.', 'twentytwelve' );
    }
    // Translators: 1 is category, 2 is tag, 3 is the date and 4 is the author's name.
    if ( $tag_list ) {
        $utility_text = __( 'This entry was posted in %1$s and tagged %2$s on %3$s<span class="by-author"> by %4$s</span>.', 'twentytwelve' );
    } elseif ( $categories_list ) {
        $utility_text = __( 'This entry was posted in %1$s on %3$s<span class="by-author"> by %4$s</span>.', 'twentytwelve' );
    } else {
        $utility_text = __( 'This entry was posted on %3$s<span class="by-author"> by %4$s</span>.', 'twentytwelve' );
    }

    printf(
        $utility_text,
        $categories_list,
        $tag_list,
        $date,
        $author
    );
}
endif;

function wareki($ymd) {
    list($y,$m,$d) = explode("/",$ymd);
    $m = str_pad($m,2,0,STR_PAD_LEFT);
    $d = str_pad($d,2,0,STR_PAD_LEFT);

    $ymd = $y.$m.$d;
    if ($ymd <= "19120729") {
        $gg = "明治";
        $yy = $y - 1867;
    } elseif ($ymd >= "19120730" && $ymd <= "19261224") {
        $gg = "大正";
        $yy = $y - 1911;
    } elseif ($ymd >= "19261225" && $ymd <= "19890107") {
        $gg = "昭和";
        $yy = $y - 1925;
    } elseif ($ymd >= "19890108") {
        $gg = "平成";
        $yy = $y - 1988;
    }
    $m = ereg_replace("^0+", "", $m);
    $d = ereg_replace("^0+", "", $d);
    $wareki = "{$gg}{$yy}年{$m}月{$d}日";
    return $wareki;
}

３．WordPressの管理画面にログインし、プラグインメニューを開くと、「wareki」がインストール済みプラグインに並んでいるはずなので、有効化する。
４．フロント側で和暦表示になっているか確かめる。

試したいというチャレンジャーな方は、以下からダウンロードください。
wareki.zip