WordPress 文章目录索引，可以方便浏览者阅读，文本分享一段最新免插件生成 WordPress 文章目索引代码，可以将 h2 – h6 段落标题自动生成文章目录索引，并可实现分层级。

把下面的代码添加至 Function.php

    // 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');

默认页面和文章中少于三个段落标题不能生成目录，代码中加了中文注释，可酌情修改。

层级显示

可以通过调整央视显示层级关系

例如： H3 为一级，H4、H5、H6 为二级

    .heading-level-4,
    .heading-level-5,
    .heading-level-6 {
    	margin-left: 40px;
    }