]*)>(.*?)<\/h\1>/i', $content, $matches, PREG_SET_ORDER);
foreach ($matches as $index => $match) {
$level = (int) $match[1]; // 2 or 3
$text = strip_tags($match[2]); // Remove any HTML tags inside heading
// Generate a clean ID from the heading text
$id = roi_generate_heading_id($text, $index);
$headings[] = array(
'level' => $level,
'text' => $text,
'id' => $id,
);
}
return $headings;
}
/**
* Generate a clean ID for a heading
*
* Creates a URL-friendly ID from heading text.
*
* @param string $text Heading text
* @param int $index Index of the heading (for uniqueness)
* @return string Clean ID
*/
function roi_generate_heading_id($text, $index) {
// Remove special characters and convert to lowercase
$id = sanitize_title($text);
// If ID is empty, use a fallback
if (empty($id)) {
$id = 'heading-' . $index;
}
return $id;
}
/**
* Generate HTML for Table of Contents
*
* Creates a nested list structure from the headings array.
*
* @param array $headings Array of headings from roi_extract_headings()
* @return string HTML for the table of contents
*/
function roi_generate_toc($headings) {
// Get minimum headings required from theme options
$min_headings = (int) roi_get_option('toc_min_headings', 2);
if (empty($headings) || count($headings) < $min_headings) {
return ''; // Don't show TOC if there are fewer headings than required
}
// Get custom TOC title from theme options
$toc_title = roi_get_toc_title();
$toc_html = '';
return $toc_html;
}
/**
* Add IDs to headings in content
*
* Modifies the post content to add ID attributes to H2 and H3 headings.
*
* @param string $content Post content
* @return string Modified content with IDs added to headings
*/
function roi_add_heading_ids($content) {
if (empty($content)) {
return $content;
}
// Extract headings first to get consistent IDs
$headings = roi_extract_headings($content);
if (empty($headings)) {
return $content;
}
// Replace headings with versions that include IDs
$heading_index = 0;
$content = preg_replace_callback(
'/]*)>(.*?)<\/h\1>/i',
function($matches) use ($headings, &$heading_index) {
if (!isset($headings[$heading_index])) {
return $matches[0];
}
$level = $matches[1];
$text = $matches[2];
$id = $headings[$heading_index]['id'];
$heading_index++;
return '' . $text . '';
},
$content
);
return $content;
}
/**
* Modify post content to add heading IDs
*
* Filters the_content to add IDs to headings for TOC linking.
*
* @param string $content Post content
* @return string Modified content
*/
function roi_filter_content_add_heading_ids($content) {
// Only apply to single posts
if (!is_single()) {
return $content;
}
return roi_add_heading_ids($content);
}
add_filter('the_content', 'roi_filter_content_add_heading_ids', 10);