Automatically Write Post Summaries in WordPress with ChatGPT

// Generate ChatGPT summary before posts

function requestChatGPTSummary($postContent) {
  $apiKey = 'sk-your_key_here'; // Add ChatGPT key here 
  $apiUrl = 'https://api.openai.com/v1/chat/completions'; 
  // Leave prompt as-is unless you are skilled with prompt engineering
  $firstQuery = 'Summarize the most important points in my blog post in under 75 words. Here are my strict guidelines: 
  - This is my article, so NEVER refer to it in the third person as "This guide", "This article", and so on; dont draw attention to the article or the author itself.  State the most important facts, options, answers, and information directly as if its general knowledge, rather than something specifically found within this piece of writing.
  - Simplify all vocabulary without oversimplifying the meaning of the content. Choose the most common, direct word that accurately conveys your meaning. Ask yourself, "Could I explain this concept to someone with a basic understanding of my industry?" If the answer is no, search for a simpler alternative. Avoid overly formal, stilted phrasing in favor of natural language patterns that feel more conversational, without skewing towards unprofessional or slang. For example, "aiming" should be "wanting", "opt" should be "choose", "For instance" should be "For example". Avoid these less common words and choose ones that are more conversational.
  - Avoid ALL words that end in the letters "ing" (also known as gerunds). Do NOT use any of these. Scan your response before sending it to me to make sure there are no words ending in "ing" anywhere in the response.
  Please respond only with the summary and no other acknowledgements or confirmations. Your reply should be less than 75 words, so focus on only the most important facts:
  -- ';
  $postData = [
    'model' => 'gpt-4', // Change as needed, use gpt-4 for best results
    'messages' => [
          [
              'role' => 'system',
              'content' => 'You are a helpful assistant.'
          ],
          [
              'role' => 'user',
              'content' => $firstQuery . $postContent
          ]
      ],
    ];
  $ch = curl_init($apiUrl);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch, CURLOPT_HTTPHEADER, [
      'Content-Type: application/json',
      'Authorization: Bearer ' . $apiKey,
  ]);
  curl_setopt($ch, CURLOPT_POST, true);
  curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($postData));
  $response = curl_exec($ch);
  curl_close($ch);
  $responseDecoded = json_decode($response, true);
  if (isset($responseDecoded['choices'][0]['message']['content'])) {
      return trim($responseDecoded['choices'][0]['message']['content']);
  } else {
      return 'Summary unavailable. Check response or configuration.';
  }
}

// Save and fetch summary from DB

function getPostSummary($postId) {
  return get_post_meta($postId, 'chatgpt_summary', true);
}
function savePostSummary($postId, $summary) {
  update_post_meta($postId, 'chatgpt_summary', $summary);
}

// Swap single quotes for double, ChatGPT likes to use 'quotes' instead of "quotes"

function swapOuterSingleQuotesForDouble($text) {
  $pattern = "/(?<=\s)'(.*?)'(?=\s|,|\.)/";
  $replacement = '"$1"';
  return preg_replace($pattern, $replacement, $text);
}
add_filter('the_content', 'custom_gpt_content_filter', 9999);
function custom_gpt_content_filter($content) {
  global $post;
  global $wpdb;
  $summary = getPostSummary($post->ID);
  // If GPT is in the query string, start the process
  if (is_single() && isset($_GET['generate-summary'])) {
    // If theres no summary yet, make one
    if (empty($summary)) {
        $summary = requestChatGPTSummary(wp_strip_all_tags($content));
        $summary = str_replace('—', '; ', $summary);
        $summary = swapOuterSingleQuotesForDouble($summary);
        savePostSummary($post->ID, $summary);
        update_post_modified_time($post->ID);
    }
  }
  
  // If a summary has already been generated in the past, lets show it
  
  if (is_single() && !empty($summary)) {
    $delete_link = '';
    if (is_user_logged_in() && current_user_can('activate_plugins')) {
      $delete_link = ' <a href="'. esc_url( get_the_permalink() ) . '?delete_gpt_post_meta='. esc_attr($post->ID) .'" 
        id="delete-gpt-post-meta" 
        onclick="return confirm(\'Are you sure you want to regenerate the GPT post meta?\')">Re-Generate ChatGPT Summary</a>';
    }
    $toc_end_position = strpos($content, '</div>', strpos($content, 'class="lwptoc"')); // This ensures it gets added after your Table of Contents. I use Lucky WP Table of Contents, which has the class "lwptoc". If you use a different one, add the class of its container here. If you don't use a Table of Contents plugin, you can ignore this.
    $summaryWithHeading = "<div class='summary'><h2>Post Summary</h2><p>$summary</p>{$delete_link}</div>";
    $content = substr_replace($content, $summaryWithHeading, strpos($content, '<h2>'), 0);
  }
  return $content;
}

// Show a "regenerate summary" link for admins only, this lets you create a new one if you don't like the one it came up with

add_action('template_redirect', 'delete_gpt_post_meta');
function delete_gpt_post_meta() {
  if (is_user_logged_in() && current_user_can('activate_plugins') && isset($_GET['delete_gpt_post_meta'])) {
    global $wpdb;
    $post_id = intval($_GET['delete_gpt_post_meta']);
    $meta_key_like = "%" . $wpdb->esc_like('gpt') . "%";
    $sql = $wpdb->prepare(
      "DELETE FROM {$wpdb->prefix}postmeta WHERE post_id = %d AND meta_key LIKE %s",
      $post_id,
      $meta_key_like
    );
    $deleted_rows = $wpdb->query($sql);
    error_log("Deleted rows count: " . $deleted_rows); 
    $current_url = remove_query_arg('delete_gpt_post_meta');
    $redirect_url = add_query_arg( 'gpt', '', $current_url );
    wp_safe_redirect($redirect_url);
    exit();
  }
}

// Update the post "modified" date after adding this since the content was updated

function update_post_modified_time($post_id){
  global $wpdb;
  $current_time = current_time('mysql');
  $current_gmt_time = current_time('mysql', 1);
  $wpdb->query(
      $wpdb->prepare(
          "UPDATE $wpdb->posts SET post_modified = %s, post_modified_gmt = %s WHERE ID = %d", 
          $current_time, 
          $current_gmt_time, 
          $post_id
      )
  );
  clean_post_cache($post_id);
}

// Cron to run this twice daily, slowly drip feed to old posts

add_action('wp', 'register_gpt_summary_preloader_event');
function register_gpt_summary_preloader_event() {
    if (!wp_next_scheduled('gpt_summary_preloader_event')) {
        wp_schedule_event(time(), 'twicedaily', 'gpt_summary_preloader_event');
    }
}
add_action('gpt_summary_preloader_event', 'execute_gpt_summary_preloader');
function execute_gpt_summary_preloader() {
    include_once(ABSPATH . 'wp-admin/includes/post.php');
    $args = array('post_type' => 'post', 'post_status' => 'publish', 'posts_per_page' => -1);
    $posts = get_posts($args);
    if (!empty($posts)) {
        $random_post = $posts[array_rand($posts)];
        $post_url = get_permalink($random_post->ID);
        $url_with_gpt = add_query_arg('generate-summary', '', $post_url);
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url_with_gpt);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_USERAGENT, 'SitePreloader'); // If you use Cloudflare, create a new rule that bypasses the cache for this user agent
        $response = curl_exec($ch);
        $httpcode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);
    }
}

?>