WordPress 文章生成目录索引

// declare a function and pass the $content as an argument
function insert_table_of_contents($content) {
	// used to determine the location of the
	// table of contents when $fixed_location is set to false
	$html_comment = \"<!--insert-toc-->\";
	// checks if $html_comment exists in $content
	$comment_found = strpos($content, $html_comment) ? true : false;
	// set to true to insert the table of contents in a fixed location
	// set to false to replace $html_comment with $table_of_contents
	$fixed_location = true;

	// return the $content if
	// $comment_found and $fixed_location are false
	if (!$fixed_location && !$comment_found) {
		return $content;
	}

	// 设置排除，默认页面文章不生成目录
	// exclude the table of contents from all pages
	// other exclusion options include:
	// in_category($id)
	// has_term($term_name)
	// is_single($array)
	// is_author($id)
    if (is_page()) {
        return $content;
    }
		
	// regex to match all HTML heading elements 2-6
	$regex = \"~(<h([2-6]))(.*?>(.*)<\\/h[2-6]>)~\";

	// preg_match_all() searches the $content using $regex patterns and
	// returns the results to $heading_results[]
	//
	// $heading_results[0][] contains all matches in full
	// $heading_results[1][] contains \'<h2-6\'
	// $heading_results[2][] contains \'2-6\'
	// $heading_results[3][] contains \'>heading title</h2-6>
	// $heading_results[4][] contains the title text
	preg_match_all($regex, $content, $heading_results);

	// 默认小于3个段落标题不生成目录
	// return $content if less than 3 heading exist in the $content
	$num_match = count($heading_results[0]);
	if($num_match < 3) {
		return $content;
	}

	// declare local variable
	$link_list = \"\";
	// loop through $heading_results
	for ($i = 0; $i < $num_match; ++ $i) {

	    // rebuild heading elements to have anchors
	    $new_heading = $heading_results[1][$i] . \" id=\'$i\' \" . $heading_results[3][$i];

	    // find original heading elements that don\'t have anchors
	    $old_heading = $heading_results[0][$i];

	    // search the $content for $old_heading and replace with $new_heading
		$content = str_replace($old_heading, $new_heading, $content);

	    // generate links for each heading element
	    // each link points to an anchor
	    $link_list .= \"<li class=\'heading-level-\" . $heading_results[2][$i] .
	    	\"\'><a href=\'#$i\'>\" . $heading_results[4][$i] . \"</a></li>\";
	}
	    
	// opening nav tag
	$start_nav = \"<nav class=\'table-of-content\'>\";
	// closing nav tag
	$end_nav = \"</nav>\";
	// title
	$title = \"<h2>Table of Contents</h2>\";

	// wrap links in \'<ul>\' element
	$link_list = \"<ul>\" . $link_list . \"</ul>\";

	// piece together the table of contents
	$table_of_contents = $start_nav . $title . $link_list . $end_nav;

	// if $fixed_location is true and
	// $comment_found is false
	// insert the table of contents at a fixed location
	if($fixed_location && !$comment_found) {
		// location of first paragraph
		$first_paragraph = strpos($content, \'</p>\', 0) + 4;
		// location of second paragraph
		$second_paragraph = strpos($content, \'</p>\', $first_p_pos);
		// insert $table_of_contents after $second_paragraph
		return substr_replace($content, $table_of_contents, $second_paragraph + 4 , 0);
	}
	// if $fixed_location is false and
	// $comment_found is true
	else {
		// replace $html_comment with the $table_of_contents
		return str_replace($html_comment, $table_of_contents, $content);
	}
}
// pass the function to the content add_filter hook
add_filter(\'the_content\', \'insert_table_of_contents\');