Pressbooks\Taxonomy::getChapterType PHP Method

    static function getChapterType($id)
    {
        $terms = get_the_terms($id, 'chapter-type');
        if ($terms && !is_wp_error($terms)) {
            foreach ($terms as $term) {
                if ('type-1' == $term->slug) {
                    return 'standard';
                } else {
                    return $term->slug;
                }
                break;
            }
        }
        return 'standard';
    }

 /**
  * @param array $book_contents
  * @param array $metadata
  */
 protected function echoPartsAndChapters($book_contents, $metadata)
 {
     $part_printf = '<div class="part %s" id="%s">';
     $part_printf .= '<div class="part-title-wrap"><h3 class="part-number">%s</h3><h1 class="part-title">%s</h1></div>%s';
     $part_printf .= '</div>';
     $chapter_printf = '<div class="chapter %s" id="%s">';
     $chapter_printf .= '<div class="chapter-title-wrap"><h3 class="chapter-number">%s</h3><h2 class="chapter-title">%s</h2></div>';
     $chapter_printf .= '<div class="ugc chapter-ugc">%s</div>%s%s';
     $chapter_printf .= '</div>';
     $s = $i = $j = 1;
     foreach ($book_contents['part'] as $part) {
         $invisibility = get_post_meta($part['ID'], 'pb_part_invisible', true) == 'on' ? 'invisible' : '';
         $part_printf_changed = '';
         $slug = $part['post_name'];
         $title = $part['post_title'];
         $part_content = trim(get_post_meta($part['ID'], 'pb_part_content', true));
         // Inject introduction class?
         if ('invisible' !== $invisibility) {
             // visible
             if (count($book_contents['part']) == 1) {
                 // only part
                 if ($part_content) {
                     // has content
                     if (!$this->hasIntroduction) {
                         $part_printf_changed = str_replace('<div class="part %s" id=', '<div class="part introduction %s" id=', $part_printf);
                         $this->hasIntroduction = true;
                     }
                 }
             } elseif (count($book_contents['part']) > 1) {
                 // multiple parts
                 if (!$this->hasIntroduction) {
                     $part_printf_changed = str_replace('<div class="part %s" id=', '<div class="part introduction %s" id=', $part_printf);
                     $this->hasIntroduction = true;
                 }
             }
         }
         // Inject part content?
         if ($part_content) {
             $part_content = $this->preProcessPostContent($part_content);
             if ($part_printf_changed) {
                 $part_printf_changed = str_replace('</h1></div>%s</div>', '</h1></div><div class="ugc part-ugc">%s</div></div>', $part_printf_changed);
             } else {
                 $part_printf_changed = str_replace('</h1></div>%s</div>', '</h1></div><div class="ugc part-ugc">%s</div></div>', $part_printf);
             }
         }
         $m = 'invisible' == $invisibility ? '' : $i;
         $my_part = sprintf($part_printf_changed ? $part_printf_changed : $part_printf, $invisibility, $slug, $m, Sanitize\decode($title), $part_content) . "\n";
         $my_chapters = '';
         foreach ($part['chapters'] as $chapter) {
             if (!$chapter['export']) {
                 continue;
                 // Skip
             }
             $chapter_printf_changed = '';
             $chapter_id = $chapter['ID'];
             $subclass = \Pressbooks\Taxonomy::getChapterType($chapter_id);
             $slug = $chapter['post_name'];
             $title = get_post_meta($chapter_id, 'pb_show_title', true) ? $chapter['post_title'] : '<span class="display-none">' . $chapter['post_title'] . '</span>';
             // Preserve auto-indexing in Prince using hidden span
             $content = $chapter['post_content'];
             $append_chapter_content = apply_filters('pb_append_chapter_content', '', $chapter_id);
             $short_title = trim(get_post_meta($chapter_id, 'pb_short_title', true));
             $subtitle = trim(get_post_meta($chapter_id, 'pb_subtitle', true));
             $author = trim(get_post_meta($chapter_id, 'pb_section_author', true));
             if (\Pressbooks\Modules\Export\Export::isParsingSubsections() == true) {
                 $sections = \Pressbooks\Book::getSubsections($chapter_id);
                 if ($sections) {
                     $content = \Pressbooks\Book::tagSubsections($content, $chapter_id);
                 }
             }
             if ($author) {
                 $content = '<h2 class="chapter-author">' . Sanitize\decode($author) . '</h2>' . $content;
             }
             if ($subtitle) {
                 $content = '<h2 class="chapter-subtitle">' . Sanitize\decode($subtitle) . '</h2>' . $content;
             }
             if ($short_title) {
                 $content = '<h6 class="short-title">' . Sanitize\decode($short_title) . '</h6>' . $content;
             }
             // Inject introduction class?
             if (!$this->hasIntroduction) {
                 $chapter_printf_changed = str_replace('<div class="chapter %s" id=', '<div class="chapter introduction %s" id=', $chapter_printf);
                 $this->hasIntroduction = true;
             }
             $n = 'numberless' == $subclass ? '' : $j;
             $my_chapters .= sprintf($chapter_printf_changed ? $chapter_printf_changed : $chapter_printf, $subclass, $slug, $n, Sanitize\decode($title), $content, $append_chapter_content, $this->doEndnotes($chapter_id)) . "\n";
             if ('numberless' !== $subclass) {
                 ++$j;
             }
         }
         // Echo with parts?
         if ('invisible' !== $invisibility) {
             // visible
             if (count($book_contents['part']) == 1) {
                 // only part
                 if ($part_content) {
                     // has content
                     echo $my_part;
                     // show
                     if ($my_chapters) {
                         echo $my_chapters;
                     }
                 } else {
                     // no content
                     if ($my_chapters) {
                         echo $my_chapters;
                     }
                 }
             } elseif (count($book_contents['part']) > 1) {
                 // multiple parts
                 if ($my_chapters) {
                     // has chapter
                     echo $my_part . $my_chapters;
                     // show
                 } else {
                     // no chapter
                     if ($part_content) {
                         // has content
                         echo $my_part;
                         // show
                     }
                 }
             }
             ++$i;
         } elseif ('invisible' == $invisibility) {
             // invisible
             if ($my_chapters) {
                 echo $my_chapters;
             }
         }
     }
 }