Added some notes on debugging WordPress sites.

notes/wordpress.md

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+# WordPress
+
+## Table of Contents
+
+- [WordPress](#wordpress)
+  - [Table of Contents](#table-of-contents)
+  - [Documentation](#documentation)
+  - [Common WordPress Errors](#common-wordpress-errors)
+  - [Debugging Steps](#debugging-steps)
+  - [Debugging Tools](#debugging-tools)
+
+## Documentation
+
+- [wp-cli](https://developer.wordpress.org/cli/commands/)
+- [Documentation Overview](https://www.wordpress.info/doc/overview/)
+- [Tutorials](https://wordpress.com/learn/)
+
+## Common WordPress Errors
+
+1. **HTTP Errors**
+
+- **404 Not Found**: Page or resource missing.
+- **403 Forbidden**: Insufficient permissions to access the resource.
+- **500 Internal Server Error**: Generic error, often caused by server misconfiguration or PHP errors.
+- **503 Service Unavailable**: Server is overloaded or in maintenance mode.
+
+2. **Database Errors**
+
+- **Error Establishing a Database Connection**: Database credentials incorrect or database server is down.
+- **Table Prefix Issues**: Wrong `$table_prefix` in `wp-config.php`.
+- **Corrupt Database**: Can be fixed using `wp db repair`.
+
+3. **PHP Errors**
+
+- **Parse Error**: Syntax error in PHP files.
+- **Fatal Error**: Missing function or class.
+- **Deprecated Function Warnings**: Old functions being used.
+
+## Debugging Steps
+
+1. **Enable Debug Mode**
+
+Edit `wp-config.php`:
+
+```php
+// Enable Debug Mode
+define('WP_DEBUG', true);
+// Enable Debug logging to the /wp-content/debug.log file
+define('WP_DEBUG_LOG', true);
+// Disable display of WordPress errors and warnings
+define('WP_DEBUG_DISPLAY', false);
+// Disable display of PHP errors and warnings
+@ini_set('display_errors', 0);
+```
+
+Logs will be saved in `wp-content/debug.log`.
+
+2. **Check `.htaccess`**
+
+Ensure WordPress rules exist:
+
+```apache
+# BEGIN WordPress
+
+<IfModule mod_rewrite.c>
+RewriteEngine On
+RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
+RewriteBase /
+RewriteRule ^index\.php$ - [L]
+RewriteCond %{REQUEST_FILENAME} !-f
+RewriteCond %{REQUEST_FILENAME} !-d
+RewriteRule . /index.php [L]
+</IfModule>
+
+# END WordPress
+```
+
+3. **Check Apache and VirtualHost config**
+
+**Redhat and derivatives**
+
+- `/etc/httpd/conf/httpd.conf`
+- `/etc/httpd/conf.d/welcome.conf`
+
+**Debian and derivatives**
+
+- `/etc/apache2/apache2.conf`
+- `/etc/apache2/sites-available/000-default.conf`
+
+```apache
+<Directory "/var/www">
+    AllowOverride All
+    # Allow open access:
+    Require all granted
+</Directory>
+<Directory "/var/www/html">
+    Options Indexes FollowSymLinks
+    AllowOverride All
+    Require all granted
+</Directory>
+```
+
+4. **Reset File Permissions**
+
+```bash
+find /var/www/html -type d -exec chmod 755 {} \;
+find /var/www/html -type f -exec chmod 644 {} \;
+```
+
+4. **Disable Plugins & Themes**
+
+Hide the plugin directory:
+
+```bash
+mv wp-content/plugins wp-content/.plugins
+```
+
+Switch to a default theme:
+
+```bash
+wp theme install twentytwentyfive --activate
+wp theme activate twentytwentyfive
+```
+
+5. **Check Server Logs**
+
+For Apache:
+
+```bash
+tail -f /var/log/httpd/error_log
+```
+
+For Nginx:
+
+```bash
+tail -f /var/log/nginx/error.log
+```
+
+6. **Verify Database Connection**
+
+```bash
+wp db check
+```
+
+If corrupt:
+
+```bash
+wp db repair
+```
+
+7. **Increase Memory Limit**
+
+Edit `wp-config.php`:
+
+```php
+define('WP_MEMORY_LIMIT', '256M');
+```
+
+## Debugging Tools
+
+- **WP-CLI**: Command-line interface for WordPress.
+- **Query Monitor**: Plugin for analyzing database queries and errors.
+- **Health Check & Troubleshooting**: Plugin for diagnosing issues.