` blocks.
  #
    $text = preg_replace_callback('{
        (?:\n\n|\A\n?)
        (             # $1 = the code block -- one or more lines, starting with a space/tab
          (?>
          [ ]{'.$this->tab_width.'}  # Lines must start with a tab or a tab-width of spaces
          .*\n+
          )+
        )
        ((?=^[ ]{0,'.$this->tab_width.'}\S)|\Z) # Lookahead for non-space at line-start, or end of doc
      }xm',
      array(&$this, '_doCodeBlocks_callback'), $text);

    return $text;
  }
  function _doCodeBlocks_callback($matches) {
    $codeblock = $matches[1];

    $codeblock = $this->outdent($codeblock);
    $codeblock = htmlspecialchars($codeblock, ENT_NOQUOTES);

    # trim leading newlines and trailing newlines
    $codeblock = preg_replace('/\A\n+|\n+\z/', '', $codeblock);

    $codeblock = "
$codeblock\n
";
    return "\n\n".$this->hashBlock($codeblock)."\n\n";
  }


  function makeCodeSpan($code) {
  #
  # Create a code span markup for $code. Called from handleSpanToken.
  #
    $code = htmlspecialchars(trim($code), ENT_NOQUOTES);
    return $this->hashPart("$code");
  }


  var $em_relist = array(
    ''  => '(?:(? '(?<=\S|^)(? '(?<=\S|^)(? '(?:(? '(?<=\S|^)(? '(?<=\S|^)(? '(?:(? '(?<=\S|^)(? '(?<=\S|^)(?em_relist as $em => $em_re) {
      foreach ($this->strong_relist as $strong => $strong_re) {
        # Construct list of allowed token expressions.
        $token_relist = array();
        if (isset($this->em_strong_relist["$em$strong"])) {
          $token_relist[] = $this->em_strong_relist["$em$strong"];
        }
        $token_relist[] = $em_re;
        $token_relist[] = $strong_re;
        
        # Construct master expression from list.
        $token_re = '{('. implode('|', $token_relist) .')}';
        $this->em_strong_prepared_relist["$em$strong"] = $token_re;
      }
    }
  }
  
  function doItalicsAndBold($text) {
    $token_stack = array('');
    $text_stack = array('');
    $em = '';
    $strong = '';
    $tree_char_em = false;
    
    while (1) {
      #
      # Get prepared regular expression for seraching emphasis tokens
      # in current context.
      #
      $token_re = $this->em_strong_prepared_relist["$em$strong"];
      
      #
      # Each loop iteration search for the next emphasis token. 
      # Each token is then passed to handleSpanToken.
      #
      $parts = preg_split($token_re, $text, 2, PREG_SPLIT_DELIM_CAPTURE);
      $text_stack[0] .= $parts[0];
      $token =& $parts[1];
      $text =& $parts[2];
      
      if (empty($token)) {
        # Reached end of text span: empty stack without emitting.
        # any more emphasis.
        while ($token_stack[0]) {
          $text_stack[1] .= array_shift($token_stack);
          $text_stack[0] .= array_shift($text_stack);
        }
        break;
      }
      
      $token_len = strlen($token);
      if ($tree_char_em) {
        # Reached closing marker while inside a three-char emphasis.
        if ($token_len == 3) {
          # Three-char closing marker, close em and strong.
          array_shift($token_stack);
          $span = array_shift($text_stack);
          $span = $this->runSpanGamut($span);
          $span = "$span";
          $text_stack[0] .= $this->hashPart($span);
          $em = '';
          $strong = '';
        } else {
          # Other closing marker: close one em or strong and
          # change current token state to match the other
          $token_stack[0] = str_repeat($token{0}, 3-$token_len);
          $tag = $token_len == 2 ? "strong" : "em";
          $span = $text_stack[0];
          $span = $this->runSpanGamut($span);
          $span = "<$tag>$span";
          $text_stack[0] = $this->hashPart($span);
          $$tag = ''; # $$tag stands for $em or $strong
        }
        $tree_char_em = false;
      } else if ($token_len == 3) {
        if ($em) {
          # Reached closing marker for both em and strong.
          # Closing strong marker:
          for ($i = 0; $i < 2; ++$i) {
            $shifted_token = array_shift($token_stack);
            $tag = strlen($shifted_token) == 2 ? "strong" : "em";
            $span = array_shift($text_stack);
            $span = $this->runSpanGamut($span);
            $span = "<$tag>$span";
            $text_stack[0] .= $this->hashPart($span);
            $$tag = ''; # $$tag stands for $em or $strong
          }
        } else {
          # Reached opening three-char emphasis marker. Push on token 
          # stack; will be handled by the special condition above.
          $em = $token{0};
          $strong = "$em$em";
          array_unshift($token_stack, $token);
          array_unshift($text_stack, '');
          $tree_char_em = true;
        }
      } else if ($token_len == 2) {
        if ($strong) {
          # Unwind any dangling emphasis marker:
          if (strlen($token_stack[0]) == 1) {
            $text_stack[1] .= array_shift($token_stack);
            $text_stack[0] .= array_shift($text_stack);
          }
          # Closing strong marker:
          array_shift($token_stack);
          $span = array_shift($text_stack);
          $span = $this->runSpanGamut($span);
          $span = "$span";
          $text_stack[0] .= $this->hashPart($span);
          $strong = '';
        } else {
          array_unshift($token_stack, $token);
          array_unshift($text_stack, '');
          $strong = $token;
        }
      } else {
        # Here $token_len == 1
        if ($em) {
          if (strlen($token_stack[0]) == 1) {
            # Closing emphasis marker:
            array_shift($token_stack);
            $span = array_shift($text_stack);
            $span = $this->runSpanGamut($span);
            $span = "$span";
            $text_stack[0] .= $this->hashPart($span);
            $em = '';
          } else {
            $text_stack[0] .= $token;
          }
        } else {
          array_unshift($token_stack, $token);
          array_unshift($text_stack, '');
          $em = $token;
        }
      }
    }
    return $text_stack[0];
  }


  function doBlockQuotes($text) {
    $text = preg_replace_callback('/
        (               # Wrap whole match in $1
        (?>
          ^[ ]*>[ ]?      # ">" at the start of a line
          .+\n          # rest of the first line
          (.+\n)*         # subsequent consecutive lines
          \n*           # blanks
        )+
        )
      /xm',
      array(&$this, '_doBlockQuotes_callback'), $text);

    return $text;
  }
  function _doBlockQuotes_callback($matches) {
    $bq = $matches[1];
    # trim one level of quoting - trim whitespace-only lines
    $bq = preg_replace('/^[ ]*>[ ]?|^[ ]+$/m', '', $bq);
    $bq = $this->runBlockGamut($bq);    # recurse

    $bq = preg_replace('/^/m', "  ", $bq);
    # These leading spaces cause problem with 
 content, 
    # so we need to fix that:
    $bq = preg_replace_callback('{(\s*
.+?
)}sx', 
      array(&$this, '_doBlockQuotes_callback2'), $bq);

    return "\n". $this->hashBlock("
\n$bq\n
")."\n\n";
  }
  function _doBlockQuotes_callback2($matches) {
    $pre = $matches[1];
    $pre = preg_replace('/^  /m', '', $pre);
    return $pre;
  }


  function formParagraphs($text) {
  #
  # Params:
  #   $text - string to process with html 
 tags
  #
    # Strip leading and trailing lines:
    $text = preg_replace('/\A\n+|\n+\z/', '', $text);

    $grafs = preg_split('/\n{2,}/', $text, -1, PREG_SPLIT_NO_EMPTY);

    #
    # Wrap 
 tags and unhashify HTML blocks
    #
    foreach ($grafs as $key => $value) {
      if (!preg_match('/^B\x1A[0-9]+B$/', $value)) {
        # Is a paragraph.
        $value = $this->runSpanGamut($value);
        $value = preg_replace('/^([ ]*)/', "
", $value);
        $value .= "
";
        $grafs[$key] = $this->unhash($value);
      }
      else {
        # Is a block.
        # Modify elements of @grafs in-place...
        $graf = $value;
        $block = $this->html_hashes[$graf];
        $graf = $block;
//        if (preg_match('{
//          \A
//          (             # $1 = 
 tag
//            
]*
//            \b
//            markdown\s*=\s*  ([\'"])  # $2 = attr quote char
//            1
//            \2
//            [^>]*
//            >
//          )
//          (             # $3 = contents
//          .*
//          )
//          (
)          # $4 = closing tag
//          \z
//          }xs', $block, $matches))
//        {
//          list(, $div_open, , $div_content, $div_close) = $matches;
//
//          # We can't call Markdown(), because that resets the hash;
//          # that initialization code should be pulled into its own sub, though.
//          $div_content = $this->hashHTMLBlocks($div_content);
//          
//          # Run document gamut methods on the content.
//          foreach ($this->document_gamut as $method => $priority) {
//            $div_content = $this->$method($div_content);
//          }
//
//          $div_open = preg_replace(
//            '{\smarkdown\s*=\s*([\'"]).+?\1}', '', $div_open);
//
//          $graf = $div_open . "\n" . $div_content . "\n" . $div_close;
//        }
        $grafs[$key] = $graf;
      }
    }

    return implode("\n\n", $grafs);
  }


  function encodeAttribute($text) {
  #
  # Encode text for a double-quoted HTML attribute. This function
  # is *not* suitable for attributes enclosed in single quotes.
  #
    $text = $this->encodeAmpsAndAngles($text);
    $text = str_replace('"', '"', $text);
    return $text;
  }
  
  
  function encodeAmpsAndAngles($text) {
  #
  # Smart processing for ampersands and angle brackets that need to 
  # be encoded. Valid character entities are left alone unless the
  # no-entities mode is set.
  #
    if ($this->no_entities) {
      $text = str_replace('&', '&', $text);
    } else {
      # Ampersand-encoding based entirely on Nat Irons's Amputator
      # MT plugin: 
      $text = preg_replace('/&(?!#?[xX]?(?:[0-9a-fA-F]+|\w+);)/', 
                '&', $text);;
    }
    # Encode remaining <'s
    $text = str_replace('<', '<', $text);

    return $text;
  }


  function doAutoLinks($text) {
    $text = preg_replace_callback('{<((https?|ftp|dict):[^\'">\s]+)>}i', 
      array(&$this, '_doAutoLinks_url_callback'), $text);

    # Email addresses: 
    $text = preg_replace_callback('{
      <
      (?:mailto:)?
      (
        (?:
          [-!#$%&\'*+/=?^_`.{|}~\w\x80-\xFF]+
        |
          ".*?"
        )
        \@
        (?:
          [-a-z0-9\x80-\xFF]+(\.[-a-z0-9\x80-\xFF]+)*\.[a-z]+
        |
          \[[\d.a-fA-F:]+\] # IPv4 & IPv6
        )
      )
      >
      }xi',
      array(&$this, '_doAutoLinks_email_callback'), $text);

    return $text;
  }
  function _doAutoLinks_url_callback($matches) {
    $url = $this->encodeAttribute($matches[1]);
    $link = "$url";
    return $this->hashPart($link);
  }
  function _doAutoLinks_email_callback($matches) {
    $address = $matches[1];
    $link = $this->encodeEmailAddress($address);
    return $this->hashPart($link);
  }


  function encodeEmailAddress($addr) {
  #
  # Input: an email address, e.g. "foo@example.com"
  #
  # Output: the email address as a mailto link, with each character
  #   of the address encoded as either a decimal or hex entity, in
  #   the hopes of foiling most address harvesting spam bots. E.g.:
  #
  #   
foo@exampl
  #        e.com
  #
  # Based by a filter by Matthew Wickline, posted to BBEdit-Talk.
  #   With some optimizations by Milian Wolff.
  #
    $addr = "mailto:" . $addr;
    $chars = preg_split('/(? $char) {
      $ord = ord($char);
      # Ignore non-ascii chars.
      if ($ord < 128) {
        $r = ($seed * (1 + $key)) % 100; # Pseudo-random function.
        # roughly 10% raw, 45% hex, 45% dec
        # '@' *must* be encoded. I insist.
        if ($r > 90 && $char != '@') /* do nothing */;
        else if ($r < 45) $chars[$key] = '&#x'.dechex($ord).';';
        else              $chars[$key] = '&#'.$ord.';';
      }
    }
    
    $addr = implode('', $chars);
    $text = implode('', array_slice($chars, 7)); # text without `mailto:`
    $addr = "$text";

    return $addr;
  }


  function parseSpan($str) {
  #
  # Take the string $str and parse it into tokens, hashing embeded HTML,
  # escaped characters and handling code spans.
  #
    $output = '';
    
    $span_re = '{
        (
          \\\\'.$this->escape_chars_re.'
        |
          (?no_markup ? '' : '
        |
             # comment
        |
          <\?.*?\?> | <%.*?%>   # processing instruction
        |
          <[/!$]?[-a-zA-Z0-9:_]+  # regular tags
          (?>
            \s
            (?>[^"\'>]+|"[^"]*"|\'[^\']*\')*
          )?
          >
      ').'
        )
        }xs';

    while (1) {
      #
      # Each loop iteration seach for either the next tag, the next 
      # openning code span marker, or the next escaped character. 
      # Each token is then passed to handleSpanToken.
      #
      $parts = preg_split($span_re, $str, 2, PREG_SPLIT_DELIM_CAPTURE);
      
      # Create token from text preceding tag.
      if ($parts[0] != "") {
        $output .= $parts[0];
      }
      
      # Check if we reach the end.
      if (isset($parts[1])) {
        $output .= $this->handleSpanToken($parts[1], $parts[2]);
        $str = $parts[2];
      }
      else {
        break;
      }
    }
    
    return $output;
  }
  
  
  function handleSpanToken($token, &$str) {
  #
  # Handle $token provided by parseSpan by determining its nature and 
  # returning the corresponding value that should replace it.
  #
    switch ($token{0}) {
      case "\\":
        return $this->hashPart("&#". ord($token{1}). ";");
      case "`":
        # Search for end marker in remaining text.
        if (preg_match('/^(.*?[^`])'.preg_quote($token).'(?!`)(.*)$/sm', 
          $str, $matches))
        {
          $str = $matches[2];
          $codespan = $this->makeCodeSpan($matches[1]);
          return $this->hashPart($codespan);
        }
        return $token; // return as text since no ending marker found.
      default:
        return $this->hashPart($token);
    }
  }


  function outdent($text) {
  #
  # Remove one level of line-leading tabs or spaces
  #
    return preg_replace('/^(\t|[ ]{1,'.$this->tab_width.'})/m', '', $text);
  }


  # String length function for detab. `_initDetab` will create a function to 
  # hanlde UTF-8 if the default function does not exist.
  var $utf8_strlen = 'mb_strlen';
  
  function detab($text) {
  #
  # Replace tabs with the appropriate amount of space.
  #
    # For each line we separate the line in blocks delemited by
    # tab characters. Then we reconstruct every line by adding the 
    # appropriate number of space between each blocks.
    
    $text = preg_replace_callback('/^.*\t.*$/m',
      array(&$this, '_detab_callback'), $text);

    return $text;
  }
  function _detab_callback($matches) {
    $line = $matches[0];
    $strlen = $this->utf8_strlen; # strlen function for UTF-8.
    
    # Split in blocks.
    $blocks = explode("\t", $line);
    # Add each blocks to the line.
    $line = $blocks[0];
    unset($blocks[0]); # Do not add first block twice.
    foreach ($blocks as $block) {
      # Calculate amount of space, insert spaces, insert block.
      $amount = $this->tab_width - 
        $strlen($line, 'UTF-8') % $this->tab_width;
      $line .= str_repeat(" ", $amount) . $block;
    }
    return $line;
  }
  function _initDetab() {
  #
  # Check for the availability of the function in the `utf8_strlen` property
  # (initially `mb_strlen`). If the function is not available, create a 
  # function that will loosely count the number of UTF-8 characters with a
  # regular expression.
  #
    if (function_exists($this->utf8_strlen)) return;
    $this->utf8_strlen = create_function('$text', 'return preg_match_all(
      "/[\\\\x00-\\\\xBF]|[\\\\xC0-\\\\xFF][\\\\x80-\\\\xBF]*/", 
      $text, $m);');
  }


  function unhash($text) {
  #
  # Swap back in all the tags hashed by _HashHTMLBlocks.
  #
    return preg_replace_callback('/(.)\x1A[0-9]+\1/', 
      array(&$this, '_unhash_callback'), $text);
  }
  function _unhash_callback($matches) {
    return $this->html_hashes[$matches[0]];
  }

}


#
# Markdown Extra Parser Class
#

class MarkdownExtra_Parser extends Markdown_Parser {

  # Prefix for footnote ids.
  var $fn_id_prefix = "";
  
  # Optional title attribute for footnote links and backlinks.
  var $fn_link_title = MARKDOWN_FN_LINK_TITLE;
  var $fn_backlink_title = MARKDOWN_FN_BACKLINK_TITLE;
  
  # Optional class attribute for footnote links and backlinks.
  var $fn_link_class = MARKDOWN_FN_LINK_CLASS;
  var $fn_backlink_class = MARKDOWN_FN_BACKLINK_CLASS;
  
  # Predefined abbreviations.
  var $predef_abbr = array();


  function __construct() {
  #
  # Constructor function. Initialize the parser object.
  #
    # Add extra escapable characters before parent constructor 
    # initialize the table.
    $this->escape_chars .= ':|';
    
    # Insert extra document, block, and span transformations. 
    # Parent constructor will do the sorting.
    $this->document_gamut += array(
      "doFencedCodeBlocks" => 5,
      "stripFootnotes"     => 15,
      "stripAbbreviations" => 25,
      "appendFootnotes"    => 50,
      );
    $this->block_gamut += array(
      "doFencedCodeBlocks" => 5,
      "doTables"           => 15,
      "doDefLists"         => 45,
      );
    $this->span_gamut += array(
      "doFootnotes"        => 5,
      "doAbbreviations"    => 70,
      );
    
    parent::Markdown_Parser();
  }
  
  
  # Extra variables used during extra transformations.
  var $footnotes = array();
  var $footnotes_ordered = array();
  var $abbr_desciptions = array();
  var $abbr_word_re = '';
  
  # Give the current footnote number.
  var $footnote_counter = 1;
  
  
  function setup() {
  #
  # Setting up Extra-specific variables.
  #
    parent::setup();
    
    $this->footnotes = array();
    $this->footnotes_ordered = array();
    $this->abbr_desciptions = array();
    $this->abbr_word_re = '';
    $this->footnote_counter = 1;
    
    foreach ($this->predef_abbr as $abbr_word => $abbr_desc) {
      if ($this->abbr_word_re)
        $this->abbr_word_re .= '|';
      $this->abbr_word_re .= preg_quote($abbr_word);
      $this->abbr_desciptions[$abbr_word] = trim($abbr_desc);
    }
  }
  
  function teardown() {
  #
  # Clearing Extra-specific variables.
  #
    $this->footnotes = array();
    $this->footnotes_ordered = array();
    $this->abbr_desciptions = array();
    $this->abbr_word_re = '';
    
    parent::teardown();
  }
  
  
  ### HTML Block Parser ###
  
  # Tags that are always treated as block tags:
  var $block_tags_re = 'p|div|h[1-6]|blockquote|pre|table|dl|ol|ul|address|form|fieldset|iframe|hr|legend';
  
  # Tags treated as block tags only if the opening tag is alone on it's line:
  var $context_block_tags_re = 'script|noscript|math|ins|del';
  
  # Tags where markdown="1" default to span mode:
  var $contain_span_tags_re = 'p|h[1-6]|li|dd|dt|td|th|legend|address';
  
  # Tags which must not have their contents modified, no matter where 
  # they appear:
  var $clean_tags_re = 'script|math';
  
  # Tags that do not need to be closed.
  var $auto_close_tags_re = 'hr|img';
  

  function hashHTMLBlocks($text) {
  #
  # Hashify HTML Blocks and "clean tags".
  #
  # We only want to do this for block-level HTML tags, such as headers,
  # lists, and tables. That's because we still want to wrap 
s around
  # "paragraphs" that are wrapped in non-block-level tags, such as anchors,
  # phrase emphasis, and spans. The list of tags we're looking for is
  # hard-coded.
  #
  # This works by calling _HashHTMLBlocks_InMarkdown, which then calls
  # _HashHTMLBlocks_InHTML when it encounter block tags. When the markdown="1" 
  # attribute is found whitin a tag, _HashHTMLBlocks_InHTML calls back
  #  _HashHTMLBlocks_InMarkdown to handle the Markdown syntax within the tag.
  # These two functions are calling each other. It's recursive!
  #
    #
    # Call the HTML-in-Markdown hasher.
    #
    list($text, ) = $this->_hashHTMLBlocks_inMarkdown($text);
    
    return $text;
  }
  function _hashHTMLBlocks_inMarkdown($text, $indent = 0, 
                    $enclosing_tag_re = '', $span = false)
  {
  #
  # Parse markdown text, calling _HashHTMLBlocks_InHTML for block tags.
  #
  # *   $indent is the number of space to be ignored when checking for code 
  #     blocks. This is important because if we don't take the indent into 
  #     account, something like this (which looks right) won't work as expected:
  #
  #     

  #         

  #         Hello World.  <-- Is this a Markdown code block or text?
  #         
  <-- Is this a Markdown code block or a real tag?
  #     

  #
  #     If you don't like this, just don't indent the tag on which
  #     you apply the markdown="1" attribute.
  #
  # *   If $enclosing_tag_re is not empty, stops at the first unmatched closing 
  #     tag with that name. Nested tags supported.
  #
  # *   If $span is true, text inside must treated as span. So any double 
  #     newline will be replaced by a single newline so that it does not create 
  #     paragraphs.
  #
  # Returns an array of that form: ( processed text , remaining text )
  #
    if ($text === '') return array('', '');

    # Regex to check for the presense of newlines around a block tag.
    $newline_before_re = '/(?:^\n?|\n\n)*$/';
    $newline_after_re = 
      '{
        ^           # Start of text following the tag.
        (?>[ ]*)?   # Optional comment.
        [ ]*\n          # Must be followed by newline.
      }xs';
    
    # Regex to match any tag.
    $block_tag_re =
      '{
        (         # $2: Capture hole tag.
                 # Tag name.
              '.$this->block_tags_re.'      |
              '.$this->context_block_tags_re.'  |
              '.$this->clean_tags_re.'          |
              (?!\s)'.$enclosing_tag_re.'
            )
            (?:
              (?=[\s"\'/a-zA-Z0-9]) # Allowed characters after tag name.
              (?>
                ".*?"   | # Double quotes (can contain `>`)
                \'.*?\'     | # Single quotes (can contain `>`)
                .+?       # Anything but quotes and `>`.
              )*?
            )?
          >         # End of tag.
        |
           # HTML Comment
        |
          <\?.*?\?> | <%.*?%> # Processing instruction
        |
           # CData Block
        |
          # Code span marker
          `+
        '. ( !$span ? ' # If not in span.
        |
          # Indented code block
          (?: ^[ ]*\n | ^ | \n[ ]*\n )
          [ ]{'.($indent+4).'}[^\n]* \n
          (?>
            (?: [ ]{'.($indent+4).'}[^\n]* | [ ]* ) \n
          )*
        |
          # Fenced code block marker
          (?> ^ | \n )
          [ ]{0,'.($indent).'}~~~+[ ]*\n
        ' : '' ). ' # End (if not is span).
        )
      }xs';

    
    $depth = 0;   # Current depth inside the tag tree.
    $parsed = ""; # Parsed text that will be returned.

    #
    # Loop through every tag until we find the closing tag of the parent
    # or loop until reaching the end of text if no parent tag specified.
    #
    do {
      #
      # Split the text using the first $tag_match pattern found.
      # Text before  pattern will be first in the array, text after
      # pattern will be at the end, and between will be any catches made 
      # by the pattern.
      #
      $parts = preg_split($block_tag_re, $text, 2, 
                PREG_SPLIT_DELIM_CAPTURE);
      
      # If in Markdown span mode, add a empty-string span-level hash 
      # after each newline to prevent triggering any block element.
      if ($span) {
        $void = $this->hashPart("", ':');
        $newline = "$void\n";
        $parts[0] = $void . str_replace("\n", $newline, $parts[0]) . $void;
      }
      
      $parsed .= $parts[0]; # Text before current tag.
      
      # If end of $text has been reached. Stop loop.
      if (count($parts) < 3) {
        $text = "";
        break;
      }
      
      $tag  = $parts[1]; # Tag to handle.
      $text = $parts[2]; # Remaining text after current tag.
      $tag_re = preg_quote($tag); # For use in a regular expression.
      
      #
      # Check for: Code span marker
      #
      if ($tag{0} == "`") {
        # Find corresponding end marker.
        $tag_re = preg_quote($tag);
        if (preg_match('{^(?>.+?|\n(?!\n))*?(?.*\n)+?[ ]{0,'.($indent).'}'.$tag_re.'[ ]*\n}', $text, 
          $matches)) 
        {
          # End marker found: pass text unchanged until marker.
          $parsed .= $tag . $matches[0];
          $text = substr($text, strlen($matches[0]));
        }
        else {
          # No end marker: just skip it.
          $parsed .= $tag;
        }
      }
      #
      # Check for: Indented code block.
      #
      else if ($tag{0} == "\n" || $tag{0} == " ") {
        # Indented code block: pass it unchanged, will be handled 
        # later.
        $parsed .= $tag;
      }
      #
      # Check for: Opening Block level tag or
      #            Opening Context Block tag (like ins and del) 
      #               used as a block tag (tag is alone on it's line).
      #
      else if (preg_match('{^<(?:'.$this->block_tags_re.')\b}', $tag) ||
        ( preg_match('{^<(?:'.$this->context_block_tags_re.')\b}', $tag) &&
          preg_match($newline_before_re, $parsed) &&
          preg_match($newline_after_re, $text)  )
        )
      {
        # Need to parse tag and following text using the HTML parser.
        list($block_text, $text) = 
          $this->_hashHTMLBlocks_inHTML($tag . $text, "hashBlock", true);
        
        # Make sure it stays outside of any paragraph by adding newlines.
        $parsed .= "\n\n$block_text\n\n";
      }
      #
      # Check for: Clean tag (like script, math)
      #            HTML Comments, processing instructions.
      #
      else if (preg_match('{^<(?:'.$this->clean_tags_re.')\b}', $tag) ||
        $tag{1} == '!' || $tag{1} == '?')
      {
        # Need to parse tag and following text using the HTML parser.
        # (don't check for markdown attribute)
        list($block_text, $text) = 
          $this->_hashHTMLBlocks_inHTML($tag . $text, "hashClean", false);
        
        $parsed .= $block_text;
      }
      #
      # Check for: Tag with same name as enclosing tag.
      #
      else if ($enclosing_tag_re !== '' &&
        # Same name as enclosing tag.
        preg_match('{^= 0);
    
    return array($parsed, $text);
  }
  function _hashHTMLBlocks_inHTML($text, $hash_method, $md_attr) {
  #
  # Parse HTML, calling _HashHTMLBlocks_InMarkdown for block tags.
  #
  # *   Calls $hash_method to convert any blocks.
  # *   Stops when the first opening tag closes.
  # *   $md_attr indicate if the use of the `markdown="1"` attribute is allowed.
  #     (it is not inside clean tags)
  #
  # Returns an array of that form: ( processed text , remaining text )
  #
    if ($text === '') return array('', '');
    
    # Regex to match `markdown` attribute inside of a tag.
    $markdown_attr_re = '
      {
        \s*     # Eat whitespace before the `markdown` attribute
        markdown
        \s*=\s*
        (?>
          (["\'])   # $1: quote delimiter   
          (.*?)   # $2: attribute value
          \1      # matching delimiter  
        |
          ([^\s>]*) # $3: unquoted attribute value
        )
        ()        # $4: make $3 always defined (avoid warnings)
      }xs';
    
    # Regex to match any tag.
    $tag_re = '{
        (         # $2: Capture hole tag.
          
                ".*?"   | # Double quotes (can contain `>`)
                \'.*?\'     | # Single quotes (can contain `>`)
                .+?       # Anything but quotes and `>`.
              )*?
            )?
          >         # End of tag.
        |
           # HTML Comment
        |
          <\?.*?\?> | <%.*?%> # Processing instruction
        |
           # CData Block
        )
      }xs';
    
    $original_text = $text;   # Save original text in case of faliure.
    
    $depth    = 0;  # Current depth inside the tag tree.
    $block_text = ""; # Temporary text holder for current text.
    $parsed   = ""; # Parsed text that will be returned.

    #
    # Get the name of the starting tag.
    # (This pattern makes $base_tag_name_re safe without quoting.)
    #
    if (preg_match('/^<([\w:$]*)\b/', $text, $matches))
      $base_tag_name_re = $matches[1];

    #
    # Loop through every tag until we find the corresponding closing tag.
    #
    do {
      #
      # Split the text using the first $tag_match pattern found.
      # Text before  pattern will be first in the array, text after
      # pattern will be at the end, and between will be any catches made 
      # by the pattern.
      #
      $parts = preg_split($tag_re, $text, 2, PREG_SPLIT_DELIM_CAPTURE);
      
      if (count($parts) < 3) {
        #
        # End of $text reached with unbalenced tag(s).
        # In that case, we return original text unchanged and pass the
        # first character as filtered to prevent an infinite loop in the 
        # parent function.
        #
        return array($original_text{0}, substr($original_text, 1));
      }
      
      $block_text .= $parts[0]; # Text before current tag.
      $tag         = $parts[1]; # Tag to handle.
      $text        = $parts[2]; # Remaining text after current tag.
      
      #
      # Check for: Auto-close tag (like 
)
      #      Comments and Processing Instructions.
      #
      if (preg_match('{^auto_close_tags_re.')\b}', $tag) ||
        $tag{1} == '!' || $tag{1} == '?')
      {
        # Just add the tag to the block as if it was text.
        $block_text .= $tag;
      }
      else {
        #
        # Increase/decrease nested tag count. Only do so if
        # the tag's name match base tag's.
        #
        if (preg_match('{^mode = $attr_m[2] . $attr_m[3];
          $span_mode = $this->mode == 'span' || $this->mode != 'block' &&
            preg_match('{^<(?:'.$this->contain_span_tags_re.')\b}', $tag);
          
          # Calculate indent before tag.
          if (preg_match('/(?:^|\n)( *?)(?! ).*?$/', $block_text, $matches)) {
            $strlen = $this->utf8_strlen;
            $indent = $strlen($matches[1], 'UTF-8');
          } else {
            $indent = 0;
          }
          
          # End preceding block with this tag.
          $block_text .= $tag;
          $parsed .= $this->$hash_method($block_text);
          
          # Get enclosing tag name for the ParseMarkdown function.
          # (This pattern makes $tag_name_re safe without quoting.)
          preg_match('/^<([\w:$]*)\b/', $tag, $matches);
          $tag_name_re = $matches[1];
          
          # Parse the content using the HTML-in-Markdown parser.
          list ($block_text, $text)
            = $this->_hashHTMLBlocks_inMarkdown($text, $indent, 
              $tag_name_re, $span_mode);
          
          # Outdent markdown text.
          if ($indent > 0) {
            $block_text = preg_replace("/^[ ]{1,$indent}/m", "", 
                          $block_text);
          }
          
          # Append tag content to parsed text.
          if (!$span_mode)  $parsed .= "\n\n$block_text\n\n";
          else        $parsed .= "$block_text";
          
          # Start over a new block.
          $block_text = "";
        }
        else $block_text .= $tag;
      }
      
    } while ($depth > 0);
    
    #
    # Hash last block text that wasn't processed inside the loop.
    #
    $parsed .= $this->$hash_method($block_text);
    
    return array($parsed, $text);
  }


  function hashClean($text) {
  #
  # Called whenever a tag must be hashed when a function insert a "clean" tag
  # in $text, it pass through this function and is automaticaly escaped, 
  # blocking invalid nested overlap.
  #
    return $this->hashPart($text, 'C');
  }


  function doHeaders($text) {
  #
  # Redefined to add id attribute support.
  #
    # Setext-style headers:
    #   Header 1  {#header1}
    #   ========
    #  
    #   Header 2  {#header2}
    #   --------
    #
    $text = preg_replace_callback(
      '{
        (^.+?)                # $1: Header text
        (?:[ ]+\{\#([-_:a-zA-Z0-9]+)\})?  # $2: Id attribute
        [ ]*\n(=+|-+)[ ]*\n+        # $3: Header footer
      }mx',
      array(&$this, '_doHeaders_callback_setext'), $text);

    # atx-style headers:
    # # Header 1        {#header1}
    # ## Header 2       {#header2}
    # ## Header 2 with closing hashes ##  {#header3}
    # ...
    # ###### Header 6   {#header2}
    #
    $text = preg_replace_callback('{
        ^(\#{1,6})  # $1 = string of #\'s
        [ ]*
        (.+?)   # $2 = Header text
        [ ]*
        \#*     # optional closing #\'s (not counted)
        (?:[ ]+\{\#([-_:a-zA-Z0-9]+)\})? # id attribute
        [ ]*
        \n+
      }xm',
      array(&$this, '_doHeaders_callback_atx'), $text);

    return $text;
  }

  private $_headerTags = array();

  function _generateHeaderID($title) {
    $base = trim(preg_replace('/[^a-z0-9]+/i', '-', strtolower(trim($title))), '-');
    $index = 1;
    $id = $base;
    while(array_key_exists($id, $this->_headerTags)) {
      $id = $base . '-' . $index;
      $index++;
    }
    $this->_headerTags[$id] = $title;
    return $id;
  }

  function _doHeaders_attr($attr, $title) {
    if (empty($attr)) {
      $id = $this->_generateHeaderID($title);
      return " id=\"$id\"";
    } else {
      $this->_headerTags[$attr] = $title;
      return " id=\"$attr\"";
    }
  }
  function _doHeaders_callback_setext($matches) {
    if ($matches[3] == '-' && preg_match('{^- }', $matches[1]))
      return $matches[0];
    $level = $matches[3]{0} == '=' ? 1 : 2;
    $attr  = $this->_doHeaders_attr($id =& $matches[2], $matches[1]);
    $block = "".$this->runSpanGamut($matches[1])."";
    return "\n" . $this->hashBlock($block) . "\n\n";
  }
  function _doHeaders_callback_atx($matches) {
    $level = strlen($matches[1]);
    $attr  = $this->_doHeaders_attr($id =& $matches[3], $matches[2]);
    $block = "".$this->runSpanGamut($matches[2])."";
    return "\n" . $this->hashBlock($block) . "\n\n";
  }


  function doTables($text) {
  #
  # Form HTML tables.
  #
    $less_than_tab = $this->tab_width - 1;
    #
    # Find tables with leading pipe.
    #
    # | Header 1 | Header 2
    # | -------- | --------
    # | Cell 1   | Cell 2
    # | Cell 3   | Cell 4
    #
    $text = preg_replace_callback('
      {
        ^             # Start of a line
        [ ]{0,'.$less_than_tab.'} # Allowed whitespace.
        [|]             # Optional leading pipe (present)
        (.+) \n           # $1: Header row (at least one pipe)
        
        [ ]{0,'.$less_than_tab.'} # Allowed whitespace.
        [|] ([ ]*[-:]+[-| :]*) \n # $2: Header underline
        
        (             # $3: Cells
          (?>
            [ ]*        # Allowed whitespace.
            [|] .* \n     # Row content.
          )*
        )
        (?=\n|\Z)         # Stop at final double newline.
      }xm',
      array(&$this, '_doTable_leadingPipe_callback'), $text);
    
    #
    # Find tables without leading pipe.
    #
    # Header 1 | Header 2
    # -------- | --------
    # Cell 1   | Cell 2
    # Cell 3   | Cell 4
    #
    $text = preg_replace_callback('
      {
        ^             # Start of a line
        [ ]{0,'.$less_than_tab.'} # Allowed whitespace.
        (\S.*[|].*) \n        # $1: Header row (at least one pipe)
        
        [ ]{0,'.$less_than_tab.'} # Allowed whitespace.
        ([-:]+[ ]*[|][-| :]*) \n  # $2: Header underline
        
        (             # $3: Cells
          (?>
            .* [|] .* \n    # Row content
          )*
        )
        (?=\n|\Z)         # Stop at final double newline.
      }xm',
      array(&$this, '_DoTable_callback'), $text);

    return $text;
  }
  function _doTable_leadingPipe_callback($matches) {
    $head   = $matches[1];
    $underline  = $matches[2];
    $content  = $matches[3];
    
    # Remove leading pipe for each row.
    $content  = preg_replace('/^ *[|]/m', '', $content);
    
    return $this->_doTable_callback(array($matches[0], $head, $underline, $content));
  }
  function _doTable_callback($matches) {
    $head   = $matches[1];
    $underline  = $matches[2];
    $content  = $matches[3];

    # Remove any tailing pipes for each line.
    $head   = preg_replace('/[|] *$/m', '', $head);
    $underline  = preg_replace('/[|] *$/m', '', $underline);
    $content  = preg_replace('/[|] *$/m', '', $content);
    
    # Reading alignement from header underline.
    $separators = preg_split('/ *[|] */', $underline);
    foreach ($separators as $n => $s) {
      if (preg_match('/^ *-+: *$/', $s))    $attr[$n] = ' align="right"';
      else if (preg_match('/^ *:-+: *$/', $s))$attr[$n] = ' align="center"';
      else if (preg_match('/^ *:-+ *$/', $s)) $attr[$n] = ' align="left"';
      else                  $attr[$n] = '';
    }
    
    # Parsing span elements, including code spans, character escapes, 
    # and inline HTML tags, so that pipes inside those gets ignored.
    $head   = $this->parseSpan($head);
    $headers  = preg_split('/ *[|] */', $head);
    $col_count  = count($headers);
    
    # Write column headers.
    $text = "\n";
    $text .= "\n";
    $text .= "\n";
    foreach ($headers as $n => $header)
      $text .= "  ".$this->runSpanGamut(trim($header))."\n";
    $text .= "\n";
    $text .= "\n";
    
    # Split content by row.
    $rows = explode("\n", trim($content, "\n"));
    
    $text .= "\n";
    foreach ($rows as $row) {
      # Parsing span elements, including code spans, character escapes, 
      # and inline HTML tags, so that pipes inside those gets ignored.
      $row = $this->parseSpan($row);
      
      # Split row by cell.
      $row_cells = preg_split('/ *[|] */', $row, $col_count);
      $row_cells = array_pad($row_cells, $col_count, '');
      
      $text .= "\n";
      foreach ($row_cells as $n => $cell)
        $text .= "  ".$this->runSpanGamut(trim($cell))."\n";
      $text .= "\n";
    }
    $text .= "\n";
    $text .= "";
    
    return $this->hashBlock($text) . "\n";
  }

  
  function doDefLists($text) {
  #
  # Form HTML definition lists.
  #
    $less_than_tab = $this->tab_width - 1;

    # Re-usable pattern to match any entire dl list:
    $whole_list_re = '(?>
      (               # $1 = whole list
        (               # $2
        [ ]{0,'.$less_than_tab.'}
        ((?>.*\S.*\n)+)       # $3 = defined term
        \n?
        [ ]{0,'.$less_than_tab.'}:[ ]+ # colon starting definition
        )
        (?s:.+?)
        (               # $4
          \z
        |
          \n{2,}
          (?=\S)
          (?!           # Negative lookahead for another term
          [ ]{0,'.$less_than_tab.'}
          (?: \S.*\n )+?      # defined term
          \n?
          [ ]{0,'.$less_than_tab.'}:[ ]+ # colon starting definition
          )
          (?!           # Negative lookahead for another definition
          [ ]{0,'.$less_than_tab.'}:[ ]+ # colon starting definition
          )
        )
      )
    )'; // mx

    $text = preg_replace_callback('{
        (?>\A\n?|(?<=\n\n))
        '.$whole_list_re.'
      }mx',
      array(&$this, '_doDefLists_callback'), $text);

    return $text;
  }
  function _doDefLists_callback($matches) {
    # Re-usable patterns to match list item bullets and number markers:
    $list = $matches[1];
    
    # Turn double returns into triple returns, so that we can make a
    # paragraph for the last item in a list, if necessary:
    $result = trim($this->processDefListItems($list));
    $result = "
\n" . $result . "\n
";
    return $this->hashBlock($result) . "\n\n";
  }


  function processDefListItems($list_str) {
  #
  # Process the contents of a single definition list, splitting it
  # into individual term and definition list items.
  #
    $less_than_tab = $this->tab_width - 1;
    
    # trim trailing blank lines:
    $list_str = preg_replace("/\n{2,}\\z/", "\n", $list_str);

    # Process definition terms.
    $list_str = preg_replace_callback('{
      (?>\A\n?|\n\n+)         # leading line
      (               # definition terms = $1
        [ ]{0,'.$less_than_tab.'} # leading whitespace
        (?![:][ ]|[ ])        # negative lookahead for a definition 
                      #   mark (colon) or more whitespace.
        (?> \S.* \n)+?        # actual term (not whitespace). 
      )     
      (?=\n?[ ]{0,3}:[ ])       # lookahead for following line feed 
                      #   with a definition mark.
      }xm',
      array(&$this, '_processDefListItems_callback_dt'), $list_str);

    # Process actual definitions.
    $list_str = preg_replace_callback('{
      \n(\n+)?            # leading line = $1
      (               # marker space = $2
        [ ]{0,'.$less_than_tab.'} # whitespace before colon
        [:][ ]+           # definition mark (colon)
      )
      ((?s:.+?))            # definition text = $3
      (?= \n+             # stop at next definition mark,
        (?:             # next term or end of text
          [ ]{0,'.$less_than_tab.'} [:][ ]  |
          
 | \z
        )           
      )         
      }xm',
      array(&$this, '_processDefListItems_callback_dd'), $list_str);

    return $list_str;
  }
  function _processDefListItems_callback_dt($matches) {
    $terms = explode("\n", trim($matches[1]));
    $text = '';
    foreach ($terms as $term) {
      $term = $this->runSpanGamut(trim($term));
      $text .= "\n
" . $term . "
";
    }
    return $text . "\n";
  }
  function _processDefListItems_callback_dd($matches) {
    $leading_line = $matches[1];
    $marker_space = $matches[2];
    $def      = $matches[3];

    if ($leading_line || preg_match('/\n{2,}/', $def)) {
      # Replace marker with the appropriate whitespace indentation
      $def = str_repeat(' ', strlen($marker_space)) . $def;
      $def = $this->runBlockGamut($this->outdent($def . "\n\n"));
      $def = "\n". $def ."\n";
    }
    else {
      $def = rtrim($def);
      $def = $this->runSpanGamut($this->outdent($def));
    }

    return "\n
" . $def . "
\n";
  }


  function doFencedCodeBlocks($text) {
  #
  # Adding the fenced code block syntax to regular Markdown:
  #
  # ~~~
  # Code block
  # ~~~
  #
    $less_than_tab = $this->tab_width;
    
    $text = preg_replace_callback('{
        (?:\n|\A)
        # 1: Opening marker
        (
          ~{3,} # Marker: three tilde or more.
        )
        [ ]* \n # Whitespace and newline following marker.
        
        # 2: Content
        (
          (?>
            (?!\1 [ ]* \n)  # Not a closing marker.
            .*\n+
          )+
        )
        
        # Closing marker.
        \1 [ ]* \n
      }xm',
      array(&$this, '_doFencedCodeBlocks_callback'), $text);

    return $text;
  }
  function _doFencedCodeBlocks_callback($matches) {
    $codeblock = $matches[2];
    $codeblock = htmlspecialchars($codeblock, ENT_NOQUOTES);
    $codeblock = preg_replace_callback('/^\n+/',
      array(&$this, '_doFencedCodeBlocks_newlines'), $codeblock);
    $codeblock = "
$codeblock
";
    return "\n\n".$this->hashBlock($codeblock)."\n\n";
  }
  function _doFencedCodeBlocks_newlines($matches) {
    return str_repeat("empty_element_suffix", 
      strlen($matches[0]));
  }


  #
  # Redefining emphasis markers so that emphasis by underscore does not
  # work in the middle of a word.
  #
  var $em_relist = array(
    ''  => '(?:(? '(?<=\S|^)(? '(?<=\S|^)(? '(?:(? '(?<=\S|^)(? '(?<=\S|^)(? '(?:(? '(?<=\S|^)(? '(?<=\S|^)(? tags
  #
    # Strip leading and trailing lines:
    $text = preg_replace('/\A\n+|\n+\z/', '', $text);
    
    $grafs = preg_split('/\n{2,}/', $text, -1, PREG_SPLIT_NO_EMPTY);

    #
    # Wrap 
 tags and unhashify HTML blocks
    #
    foreach ($grafs as $key => $value) {
      $value = trim($this->runSpanGamut($value));
      
      # Check if this should be enclosed in a paragraph.
      # Clean tag hashes & block tag hashes are left alone.
      $is_p = !preg_match('/^B\x1A[0-9]+B|^C\x1A[0-9]+C$/', $value);
      
      if ($is_p) {
        $value = "
$value
";
      }
      $grafs[$key] = $value;
    }
    
    # Join grafs in one text, then unhash HTML tags. 
    $text = implode("\n\n", $grafs);
    
    # Finish by removing any tag hashes still present in $text.
    $text = $this->unhash($text);
    
    return $text;
  }
  
  
  ### Footnotes
  
  function stripFootnotes($text) {
  #
  # Strips link definitions from text, stores the URLs and titles in
  # hash references.
  #
    $less_than_tab = $this->tab_width - 1;

    # Link defs are in the form: [^id]: url "optional title"
    $text = preg_replace_callback('{
      ^[ ]{0,'.$less_than_tab.'}\[\^(.+?)\][ ]?:  # note_id = $1
        [ ]*
        \n?         # maybe *one* newline
      (           # text = $2 (no blank lines allowed)
        (?:         
          .+        # actual text
        |
          \n        # newlines but 
          (?!\[\^.+?\]:\s)# negative lookahead for footnote marker.
          (?!\n+[ ]{0,3}\S)# ensure line is not blank and followed 
                  # by non-indented content
        )*
      )   
      }xm',
      array(&$this, '_stripFootnotes_callback'),
      $text);
    return $text;
  }
  function _stripFootnotes_callback($matches) {
    $note_id = $this->fn_id_prefix . $matches[1];
    $this->footnotes[$note_id] = $this->outdent($matches[2]);
    return ''; # String that will replace the block
  }


  function doFootnotes($text) {
  #
  # Replace footnote references in $text [^id] with a special text-token 
  # which will be replaced by the actual footnote marker in appendFootnotes.
  #
    if (!$this->in_anchor) {
      $text = preg_replace('{\[\^(.+?)\]}', "F\x1Afn:\\1\x1A:", $text);
    }
    return $text;
  }

  
  function appendFootnotes($text) {
  #
  # Append footnote list to text.
  #
    $text = preg_replace_callback('{F\x1Afn:(.*?)\x1A:}', 
      array(&$this, '_appendFootnotes_callback'), $text);
  
    if (!empty($this->footnotes_ordered)) {
      $text .= "\n\n";
      $text .= "
\n";
      $text .= "empty_element_suffix ."\n";
      $text .= "
\n\n";
      
      $attr = " rev=\"footnote\"";
      if ($this->fn_backlink_class != "") {
        $class = $this->fn_backlink_class;
        $class = $this->encodeAttribute($class);
        $attr .= " class=\"$class\"";
      }
      if ($this->fn_backlink_title != "") {
        $title = $this->fn_backlink_title;
        $title = $this->encodeAttribute($title);
        $attr .= " title=\"$title\"";
      }
      $num = 0;
      
      while (!empty($this->footnotes_ordered)) {
        $footnote = reset($this->footnotes_ordered);
        $note_id = key($this->footnotes_ordered);
        unset($this->footnotes_ordered[$note_id]);
        
        $footnote .= "\n"; # Need to append newline before parsing.
        $footnote = $this->runBlockGamut("$footnote\n");        
        $footnote = preg_replace_callback('{F\x1Afn:(.*?)\x1A:}', 
          array(&$this, '_appendFootnotes_callback'), $footnote);
        
        $attr = str_replace("%%", ++$num, $attr);
        $note_id = $this->encodeAttribute($note_id);
        
        # Add backlink to last paragraph; create new paragraph if needed.
        $backlink = "↩";
        if (preg_match('{
$}', $footnote)) {
          $footnote = substr($footnote, 0, -4) . " $backlink
";
        } else {
          $footnote .= "\n\n
$backlink
";
        }
        
        $text .= "
\n";
        $text .= $footnote . "\n";
        $text .= "
\n\n";
      }
      
      $text .= "
\n";
      $text .= "
";
    }
    return $text;
  }
  function _appendFootnotes_callback($matches) {
    $node_id = $this->fn_id_prefix . $matches[1];
    
    # Create footnote marker only if it has a corresponding footnote *and*
    # the footnote hasn't been used by another marker.
    if (isset($this->footnotes[$node_id])) {
      # Transfert footnote content to the ordered list.
      $this->footnotes_ordered[$node_id] = $this->footnotes[$node_id];
      unset($this->footnotes[$node_id]);
      
      $num = $this->footnote_counter++;
      $attr = " rel=\"footnote\"";
      if ($this->fn_link_class != "") {
        $class = $this->fn_link_class;
        $class = $this->encodeAttribute($class);
        $attr .= " class=\"$class\"";
      }
      if ($this->fn_link_title != "") {
        $title = $this->fn_link_title;
        $title = $this->encodeAttribute($title);
        $attr .= " title=\"$title\"";
      }
      
      $attr = str_replace("%%", $num, $attr);
      $node_id = $this->encodeAttribute($node_id);
      
      return
        "".
        "$num".
        "";
    }
    
    return "[^".$matches[1]."]";
  }
    
  
  ### Abbreviations ###
  
  function stripAbbreviations($text) {
  #
  # Strips abbreviations from text, stores titles in hash references.
  #
    $less_than_tab = $this->tab_width - 1;

    # Link defs are in the form: [id]*: url "optional title"
    $text = preg_replace_callback('{
      ^[ ]{0,'.$less_than_tab.'}\*\[(.+?)\][ ]?:  # abbr_id = $1
      (.*)          # text = $2 (no blank lines allowed)  
      }xm',
      array(&$this, '_stripAbbreviations_callback'),
      $text);
    return $text;
  }
  function _stripAbbreviations_callback($matches) {
    $abbr_word = $matches[1];
    $abbr_desc = $matches[2];
    if ($this->abbr_word_re)
      $this->abbr_word_re .= '|';
    $this->abbr_word_re .= preg_quote($abbr_word);
    $this->abbr_desciptions[$abbr_word] = trim($abbr_desc);
    return ''; # String that will replace the block
  }
  
  
  function doAbbreviations($text) {
  #
  # Find defined abbreviations in text and wrap them in  elements.
  #
    if ($this->abbr_word_re) {
      // cannot use the /x modifier because abbr_word_re may 
      // contain significant spaces:
      $text = preg_replace_callback('{'.
        '(?abbr_word_re.')'.
        '(?![\w\x1A])'.
        '}', 
        array(&$this, '_doAbbreviations_callback'), $text);
    }
    return $text;
  }
  function _doAbbreviations_callback($matches) {
    $abbr = $matches[0];
    if (isset($this->abbr_desciptions[$abbr])) {
      $desc = $this->abbr_desciptions[$abbr];
      if (empty($desc)) {
        return $this->hashPart("$abbr");
      } else {
        $desc = $this->encodeAttribute($desc);
        return $this->hashPart("$abbr");
      }
    } else {
      return $matches[0];
    }
  }

}


/*

PHP Markdown Extra
==================

Description
-----------

This is a PHP port of the original Markdown formatter written in Perl 
by John Gruber. This special "Extra" version of PHP Markdown features 
further enhancements to the syntax for making additional constructs 
such as tables and definition list.

Markdown is a text-to-HTML filter; it translates an easy-to-read /
easy-to-write structured text format into HTML. Markdown's text format
is most similar to that of plain text email, and supports features such
as headers, *emphasis*, code blocks, blockquotes, and links.

Markdown's syntax is designed not as a generic markup language, but
specifically to serve as a front-end to (X)HTML. You can use span-level
HTML tags anywhere in a Markdown document, and you can use block level
HTML tags (like 
 and  as well).

For more information about Markdown's syntax, see:




Bugs
----

To file bug reports please send email to:



Please include with your report: (1) the example input; (2) the output you
expected; (3) the output Markdown actually produced.


Version History
--------------- 

See the readme file for detailed release notes for this version.


Copyright and License
---------------------

PHP Markdown & Extra  
Copyright (c) 2004-2009 Michel Fortin  
  
All rights reserved.

Based on Markdown  
Copyright (c) 2003-2006 John Gruber   
   
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

* Redistributions of source code must retain the above copyright notice,
  this list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.

* Neither the name "Markdown" nor the names of its contributors may
  be used to endorse or promote products derived from this software
  without specific prior written permission.

This software is provided by the copyright holders and contributors "as
is" and any express or implied warranties, including, but not limited
to, the implied warranties of merchantability and fitness for a
particular purpose are disclaimed. In no event shall the copyright owner
or contributors be liable for any direct, indirect, incidental, special,
exemplary, or consequential damages (including, but not limited to,
procurement of substitute goods or services; loss of use, data, or
profits; or business interruption) however caused and on any theory of
liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this
software, even if advised of the possibility of such damage.

*/
?>