wp_get_document_title自定义页面title标签

因为服务器配置的问题，之前一直用的3.6.1版本的wordpress，眼看这阿里云服务器快要到期，暂时也不准备续费，想把wp博客搬到目前所使用的天翼云服务器上，天翼云的服务器安装的php版本是7.2，尝试了多个wordpress 3.x版本均无法正确识别，于是只能换成了4.5.28版本的wordpress。

这几天一边查百度，一边复制粘贴尝试订制一个自用的主题，才进入head部分就已经举步维艰，看了一下空白页的源代码，3.6.1版本正常生效的tltle标签，在4.5.28版本里变成了空白。

原因是wp_title( )这个函数已经被放弃使用了，自4.4.0版本之后，wordpress提供了新的wp_get_document_title( )函数来生成tltle标签。尝试了一下效果，默认的连接符号也从“|”变成了“-”。

wp_get_document_title()的源码

function wp_get_document_title() {

    /**
     * Filters the document title before it is generated.
     *
     * Passing a non-empty value will short-circuit wp_get_document_title(),
     * returning that value instead.
     *
     * @since 4.4.0
     *
     * @param string $title The document title. Default empty string.
     */
    $title = apply_filters( 'pre_get_document_title', '' );
    if ( ! empty( $title ) ) {
        return $title;
    }

    global $page, $paged;

    $title = array(
        'title' => '',
    );

    // If it's a 404 page, use a "Page not found" title.
    if ( is_404() ) {
        $title['title'] = __( 'Page not found' );

        // If it's a search, use a dynamic search results title.
    } elseif ( is_search() ) {
        /* translators: %s: Search query. */
        $title['title'] = sprintf( __( 'Search Results for “%s”' ), get_search_query() );

        // If on the front page, use the site title.
    } elseif ( is_front_page() ) {
        $title['title'] = get_bloginfo( 'name', 'display' );

        // If on a post type archive, use the post type archive title.
    } elseif ( is_post_type_archive() ) {
        $title['title'] = post_type_archive_title( '', false );

        // If on a taxonomy archive, use the term title.
    } elseif ( is_tax() ) {
        $title['title'] = single_term_title( '', false );

        /*
        * If we're on the blog page that is not the homepage
        * or a single post of any post type, use the post title.
        */
    } elseif ( is_home() || is_singular() ) {
        $title['title'] = single_post_title( '', false );

        // If on a category or tag archive, use the term title.
    } elseif ( is_category() || is_tag() ) {
        $title['title'] = single_term_title( '', false );

        // If on an author archive, use the author's display name.
    } elseif ( is_author() && get_queried_object() ) {
        $author         = get_queried_object();
        $title['title'] = $author->display_name;

        // If it's a date archive, use the date as the title.
    } elseif ( is_year() ) {
        $title['title'] = get_the_date( _x( 'Y', 'yearly archives date format' ) );

    } elseif ( is_month() ) {
        $title['title'] = get_the_date( _x( 'F Y', 'monthly archives date format' ) );

    } elseif ( is_day() ) {
        $title['title'] = get_the_date();
    }

    // Add a page number if necessary.
    if ( ( $paged >= 2 || $page >= 2 ) && ! is_404() ) {
        /* translators: %s: Page number. */
        $title['page'] = sprintf( __( 'Page %s' ), max( $paged, $page ) );
    }

    // Append the description or site title to give context.
    if ( is_front_page() ) {
        $title['tagline'] = get_bloginfo( 'description', 'display' );
    } else {
        $title['site'] = get_bloginfo( 'name', 'display' );
    }

    /**
     * Filters the separator for the document title.
     *
     * @since 4.4.0
     *
     * @param string $sep Document title separator. Default '-'.
     */
    $sep = apply_filters( 'document_title_separator', '-' );

    /**
     * Filters the parts of the document title.
     *
     * @since 4.4.0
     *
     * @param array $title {
     *     The document title parts.
     *
     *     @type string $title   Title of the viewed page.
     *     @type string $page    Optional. Page number if paginated.
     *     @type string $tagline Optional. Site description when on home page.
     *     @type string $site    Optional. Site title when not on home page.
     * }
     */
    $title = apply_filters( 'document_title_parts', $title );

    $title = implode( " $sep ", array_filter( $title ) );

    /**
     * Filters the document title.
     *
     * @since 5.8.0
     *
     * @param string $title Document title.
     */
    $title = apply_filters( 'document_title', $title );

    return $title;
}