使用PHP编译Markdown成为HTML代码的基本思路

Github Reference: https://github.com/SegmentFault/HyperDown
原文标题：使用PHP编译Markdown成为HTML代码的基本思路
原文地址：https://www.jianshu.com/p/c71257080201

1. 从前端获得Markdown原始数据:

   $s_markdown = $this->input->expectType('p:markdown', 'string', '');
   

2. 将原文中的水平制表符\t替换成空格,去除换行符\r:

   private function initText($text) {
   $text = str_replace(array("\t", "\r"), array(' ', ''), $text);
   return $text;
   }
   

3. 处理所有的Mark符号,转变为HTML标签(例):

   $text = preg_replace_callback( "/!\[((?:[^\]]|\\\\\]|\\\\\[)*?)\]\(((?:[^\)]|\\\\\)|\\\\\()+?)\)/",
   function ($matches) use ($self){
   $escaped = $self->escapeBracket($matches[1]);
   $url = $self->escapeBracket($matches[2]);
   $url = $self->cleanUrl($url);
   return $self->makeHolder( "<img src=\"{$url}\" alt=\"{$escaped}\" title=\"{$escaped}\">" ); },
   $text );
   

4. 添加脚注:

   $html .= '<div class="footnotes"><hr><ol>';
   $index = 1;
   while ($val = array_shift($this->_footnotes))
   {
   if (is_string($val)){
       $val .= " <a href=\"#fnref-{$index}\" class=\"footnote-backref\"></a>";
   }else{
       $val[count($val) - 1] .= " <a href=\"#fnref-{$index}\" class=\"footnote-backref\"></a>";
       $val = count($val) > 1 ? $this->parse(implode("\n", $val)) : $this->parseInline($val[0]);
   }
   $html .= "<li id=\"fn-{$index}\">{$val}</li>"; $index ++;
   }
   $html .= '</ol></div>';
   

5. 将以上转换方法声明为重载函数,递归调用:

   public function makeHtml($text)
   {
   $text = $this->initText($text);
   $html = $this->parse($text);
   $html = $this->makeFootnotes($html);
   return $this->call('makeHtml', $html);
   }