php - 在 php 中从 Markdown 生成目录

Question

我想用 Markdown 创建一个目录。
例如在 stackedit.io https://stackedit.io/editor#table-of-contents当你插入时:

[TOC]

有什么方法可以从 Markdown 中生成这个吗？

例如如果你有:

## header 1
## header 2

目录应该是:

<ol>
   <li><a href="#header1">Header 1</a></li>
   <li><a href="#header2">Header 2</a></li>
</ol>

我是否应该创建自己的 Markdown 解析器来获取 ToC？

Answer 1

以下是一个完成基本工作的函数:它返回找到的标题的 JSON 列表，每个标题都有其级别和文本。
此 JSON 元素可进一步用于生成所需的 HTML 结构或任何其他内容。

它的工作原理是这样的:

1. 获取字符串形式的 markdown 文件，并将换行符规范化为仅 \n (这对下面的第 3 步很重要)
2. 应用一个简单的正则表达式 /^(?:=|-|#).*$/m与 PREG_OFFSET_CAPTURE : so 匹配符合以下任一条件的所有行:
   • 是<h1>的“下划线” (当“=”时)或 <h2> (当“-”时)标题
   • 是标题本身(以“#”开头)
3. 迭代匹配的行:
   • 对于“下划线”，查看前一行的源文件，位于当前行偏移量和前一个换行符之间的字符串；然后从下划线类型和上一行的文本中获取级别
   • 否则只需从当前行本身获取级别和文本

函数如下:

function markdown_toc($file_path) {
  $file = file_get_contents($file_path);

  // ensure using only "\n" as line-break
  $source = str_replace(["\r\n", "\r"], "\n", $file);

  // look for markdown TOC items
  preg_match_all(
    '/^(?:=|-|#).*$/m',
    $source,
    $matches,
    PREG_PATTERN_ORDER | PREG_OFFSET_CAPTURE
  );

  // preprocess: iterate matched lines to create an array of items
  // where each item is an array(level, text)
  $file_size = strlen($source);
  foreach ($matches[0] as $item) {
    $found_mark = substr($item[0], 0, 1);
    if ($found_mark == '#') {
      // text is the found item
      $item_text = $item[0];
      $item_level = strrpos($item_text, '#') + 1;
      $item_text = substr($item_text, $item_level);
    } else {
      // text is the previous line (empty if <hr>)
      $item_offset = $item[1];
      $prev_line_offset = strrpos($source, "\n", -($file_size - $item_offset + 2));
      $item_text =
        substr($source, $prev_line_offset, $item_offset - $prev_line_offset - 1);
      $item_text = trim($item_text);
      $item_level = $found_mark == '=' ? 1 : 2;
    }
    if (!trim($item_text) OR strpos($item_text, '|') !== FALSE) {
      // item is an horizontal separator or a table header, don't mind
      continue;
    }
    $raw_toc[] = ['level' => $item_level, 'text' => trim($item_text)];
  }

  // create a JSON list (the easiest way to generate HTML structure is using JS)
  return json_encode($raw_toc);
}

这是它从 home page of the link you provided 返回的结果:

[
  {"level":1,"text":"Welcome to StackEdit!"},
  {"level":2,"text":"Documents"},
  {"level":4,"text":"<\/i> Create a document"},
  {"level":4,"text":"<\/i> Switch to another document"},
  {"level":4,"text":"<\/i> Rename a document"},
  {"level":4,"text":"<\/i> Delete a document"},
  {"level":4,"text":"<\/i> Export a document"},
  {"level":2,"text":"Synchronization"},
  {"level":4,"text":"<\/i> Open a document"},
  {"level":4,"text":"<\/i> Save a document"},
  {"level":4,"text":"<\/i> Synchronize a document"},
  {"level":4,"text":"<\/i> Manage document synchronization"},
  {"level":2,"text":"Publication"},
  {"level":4,"text":"<\/i> Publish a document"},
  {"level":2,"text":"- Markdown, to publish the Markdown text on a website that can interpret it (**GitHub** for instance),"},
  {"level":2,"text":"- HTML, to publish the document converted into HTML (on a blog for example),"},
  {"level":4,"text":"<\/i> Update a publication"},
  {"level":4,"text":"<\/i> Manage document publication"},
  {"level":2,"text":"Markdown Extra"},
  {"level":3,"text":"Tables"},
  {"level":3,"text":"Definition Lists"},
  {"level":3,"text":"Fenced code blocks"},
  {"level":3,"text":"Footnotes"},
  {"level":3,"text":"SmartyPants"},
  {"level":3,"text":"Table of contents"},
  {"level":3,"text":"MathJax"},
  {"level":3,"text":"UML diagrams"},
  {"level":3,"text":"Support StackEdit"}
]