如何对 html 中的元素进行子字符串化

Question

我需要缩短 WP 主题中 previous 和 next 按钮中的 title。

代码如下：

    <?php

    /* ----------------------------------------------------------------------------------
        Display navigation to next/previous pages when applicable.
    ---------------------------------------------------------------------------------- */
    if ( ! function_exists( 'thinkup_input_nav' ) ) :
    function thinkup_input_nav( $nav_id ) {

    global $wp_query, $post;

        // Don't print empty markup on single pages if there's nowhere to navigate.
        if ( is_single() ) {
            $previous = ( is_attachment() ) ? get_post( $post->post_parent ) : get_adjacent_post( false, '', true );
            $next = get_adjacent_post( false, '', false );

            if ( ! $next && ! $previous )
                return;
        }

        // Don't print empty markup in archives if there's only one page.
        if ( $wp_query->max_num_pages < 2 && ( is_home() || is_archive() || is_search() ) )
            return;

        ?>
        <nav role="navigation" id="<?php echo $nav_id; ?>">
        <?php if ( is_single() ) : ?>

            <?php previous_post_link( '<div class="nav-previous">%link</div>', '<span class="meta-icon"><i class="icon-angle-left icon-large"></i></span><span class="meta-nav">%title</span>' ); ?>
            <?php next_post_link( '<div class="nav-next">%link</div>', '<span class="meta-nav">%title</span><span class="meta-icon"><i class="icon-angle-right icon-large"></i></span>' ); ?>

        <?php elseif ( $wp_query->max_num_pages > 1 && ( is_home() || is_archive() || is_search() ) ) : // navigation links for home, archive, and search pages ?>

            <?php if ( get_next_posts_link() ) : ?>
            <div class="nav-previous"><?php next_posts_link( __( 'Older posts', 'lan-thinkupthemes') ); ?></div>
            <?php endif; ?>

            <?php if ( get_previous_posts_link() ) : ?>
            <div class="nav-next"><?php previous_posts_link( __( 'Newer posts', 'lan-thinkupthemes') ); ?></div>
            <?php endif; ?>

        <?php endif; ?>

        </nav><!-- #<?php echo $nav_id; ?> -->
        <?php

    }
    endif; 


    /* ----------------------------------------------------------------------------------
        Display navigation to next/previous image when applicable.
    ---------------------------------------------------------------------------------- */
    if ( ! function_exists( 'thinkup_input_imagesnav' ) ) :
    function thinkup_input_imagesnav() {

    global $wp_query, $post;
        ?>

        <nav role="navigation" id="nav-below">
            <div class="nav-previous"><?php previous_image_link( 'false', '<div class="nav-previous"><span class="meta-icon"><i class="icon-angle-left icon-large"></i></span><span class="meta-nav">' . __( 'Previous', 'lan-thinkupthemes') . ' </span></div>' ); ?></div>
            <div class="nav-next"><?php next_image_link( 'false', '<span class="meta-nav">' . __( 'Next', 'lan-thinkupthemes') . '</span><span class="meta-icon"><i class="icon-angle-right icon-large"></i></span>' ); ?></div>
        </nav><!-- #image-navigation -->

    <?php

    }
    endif;


    /* Display comments at bottom of post, page and project pages. */
    function thinkup_input_allowcomments() {
        if ( comments_open() || '0' != get_comments_number() )
            comments_template( '/comments.php', true );
    }


    /* ----------------------------------------------------------------------------------
        Returns true if a blog has more than 1 category.
    ---------------------------------------------------------------------------------- */
    function thinkup_input_categorizedblog() {
        if ( false === ( $all_the_cool_cats = get_transient( 'all_the_cool_cats' ) ) ) {
            // Create an array of all the categories that are attached to posts
            $all_the_cool_cats = get_categories( array(
                'hide_empty' => 1,
            ) );

            // Count the number of categories that are attached to the posts
            $all_the_cool_cats = count( $all_the_cool_cats );

            set_transient( 'all_the_cool_cats', $all_the_cool_cats );
        }

        if ( '1' != $all_the_cool_cats ) {
            return true;
        } else {
            return false;
        }
    }

    /* Flush out the transients used in thinkup_input_categorizedblog. */
    function thinkup_input_transient_flusher() {
        delete_transient( 'all_the_cool_cats' );
    }
    add_action( 'edit_category', 'thinkup_input_transient_flusher' );
    add_action( 'save_post', 'thinkup_input_transient_flusher' );

我尝试的是向这一行添加子字符串：

<?php previous_post_link( '<div class="nav-previous">%link</div>', '<span class="meta-icon"><i class="icon-angle-left icon-large"></i></span><span class="meta-nav">%title</span>' ); ?>

至：

<?php previous_post_link( '<div class="nav-previous">%link</div>', '<span class="meta-icon"><i class="icon-angle-left icon-large"></i></span><span class="meta-nav"><?php echo substr(%title,0,10)?></span>' ); ?>

但在重新加载页面时，它显示的是一个空文本。

我做错了什么？

Answer 1

您可以覆盖 functions.php 主题文件中的 previous_post_link() 函数，如下所示：

function previous_post_link($format='&laquo; %link', $link='%title', $in_same_cat = false, $excluded_categories = '',$limit = -1) {

    if ( is_attachment() )
        $post = & get_post($GLOBALS['post']->post_parent);
    else
        $post = get_previous_post($in_same_cat, $excluded_categories);

    if ( !$post )
        return;

    $title = apply_filters('the_title', $post->post_title, $post);
    if ($limit>-1) {$title = substr($title,0,$limit).'&hellip;';}
    $string = '<a href="'.get_permalink($post->ID).'">';
    $link = str_replace('%title', $title, $link);
    $link = $pre . $string . $link . '</a>';

    $format = str_replace('%link', $link, $format);

    echo $format;

然后您可以调用带有附加参数的函数来定义您想要的 trim 长度：

<li><?php previous_post_link('%link','&laquo %title',FALSE,'',20); ?></li>

希望对您有所帮助。摘自 https://wordpress.org/support/topic/using-substr-to-limit-characters-in-post-title

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