WordPress自定义路由无法返回数据库数据问题求助

Hey Jake, let's break down how to troubleshoot this step by step—since you're new to WordPress, I'll keep things clear and actionable!

Since your request isn't throwing a 404, the endpoint is reachable, but we need to make sure it's configured to return data properly.

• Double-check your register_rest_route setup. You must use WordPress's REST response functions instead of just returning an array or echoing content. For example:

  // Correct endpoint registration example
  add_action('rest_api_init', function() {
      register_rest_route(
          'my-library/v1', // Your custom namespace
          '/index-data/', // Your endpoint route
          array(
              'methods' => 'GET',
              'callback' => 'fetch_library_index_data',
              'permission_callback' => '__return_true', // Temp: allow all access for testing
          )
      );
  });
  
  // Callback function with proper response handling
  function fetch_library_index_data() {
      global $wpdb; // Critical: access WordPress's database object
      $table_name = 'saic3_LibraryIndex'; // Use full table name if prefix isn't part of it
  
      // Run your query
      $results = $wpdb->get_results("SELECT * FROM $table_name");
  
      // Check for database errors
      if ($wpdb->last_error) {
          return new WP_Error('db_query_failed', $wpdb->last_error, array('status' => 500));
      }
  
      // Return valid REST response
      return rest_ensure_response($results);
  }
  

• Make sure your Ajax request URL matches the endpoint path (e.g., wp-json/my-library/v1/index-data).

Empty results often come from a query that's not pulling data correctly:

• Confirm the table exists and has data: Log into phpMyAdmin (or your database tool) and run SELECT * FROM saic3_LibraryIndex directly. If there's no data here, that's the root issue!
• Check the $wpdb reference: You must declare global $wpdb; in your callback function—without it, WordPress can't access the database.
• Debug the query error: Add var_dump($wpdb->last_error); inside your callback to see if the query is failing (enable WP_DEBUG to see this output).

Use your browser's DevTools (F12 → Network tab) to dig into the request:

• Look at the Response and Preview tabs for the Ajax call. Is it returning an empty array, an error message, or nothing at all?
• Ensure your JS is handling the response correctly. Here's a solid example:

  document.addEventListener('DOMContentLoaded', function() {
      fetch('/wp-json/my-library/v1/index-data')
          .then(response => {
              if (!response.ok) throw new Error(`HTTP error! Status: ${response.status}`);
              return response.json();
          })
          .then(data => {
              console.log('Fetched data:', data); // Check console for results first
              // Add your page-populating logic here
          })
          .catch(error => console.error('Fetch failed:', error));
  });
  

Turn on debugging to catch hidden errors:

• Open your wp-config.php file and add these lines:

  define('WP_DEBUG', true);
  define('WP_DEBUG_LOG', true);
  

• Errors will log to wp-content/debug.log—this can reveal issues with your query or endpoint code that aren't showing up in the browser.

内容的提问来源于stack exchange，提问作者Jake