Answer by Deepthink

To migrate WordPress from a local MySQL server to Google Cloud SQL, update the following in the wp-config.php file:

1. Database Host (DB_HOST)
   Replace 'localhost' with the Cloud SQL instance's IP address or connection name (if using the Cloud SQL Proxy).

   • Public IP: Use the instance's public IP (e.g., '123.456.789.0').
   • Private IP (GCP VPC): Use the private IP.
   • Cloud SQL Proxy: Use the socket path (e.g., 'localhost:/cloudsql/project-id:region:instance-id').

2. Database Name (DB_NAME)
   Set to the database name created in Cloud SQL (e.g., 'wordpress_db').

3. Database User (DB_USER)
   Set to the Cloud SQL username (e.g., 'wp_user').

4. Database Password (DB_PASSWORD)
   Set to the Cloud SQL user's password (e.g., 'secure_password').

5. (Optional) SSL Configuration
   If enforcing SSL, add these lines (adjust paths to your certificate files):

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   define( 'MYSQL_CLIENT_FLAGS', MYSQLI_CLIENT_SSL );
   define( 'MYSQL_SSL_CA', '/path/to/server-ca.pem' );
   define( 'MYSQL_SSL_CERT', '/path/to/client-cert.pem' );
   define( 'MYSQL_SSL_KEY', '/path/to/client-key.pem' );

Example Configuration:

// Before
define( 'DB_HOST', 'localhost' );

// After (using public IP)
define( 'DB_NAME', 'wordpress_db' );
define( 'DB_USER', 'wp_cloud_user' );
define( 'DB_PASSWORD', 'your_secure_password' );
define( 'DB_HOST', '203.0.113.10' ); // Cloud SQL public IP

// Optional SSL (uncomment if needed)
// define( 'MYSQL_CLIENT_FLAGS', MYSQLI_CLIENT_SSL );
// define( 'MYSQL_SSL_CA', '/var/www/ssl/server-ca.pem' );
// define( 'MYSQL_SSL_CERT', '/var/www/ssl/client-cert.pem' );
// define( 'MYSQL_SSL_KEY', '/var/www/ssl/client-key.pem' );

Additional Steps:

• Authorize WordPress Server IP: In Cloud SQL, whitelist the server's IP under Connections > Networking > Authorized Networks (for public IP).
• Use Cloud SQL Proxy: For enhanced security, deploy the proxy and configure DB_HOST to use the proxy socket.
• Test Connectivity: Verify the WordPress server can connect to Cloud SQL (e.g., using mysql -h [IP] -u [user] -p).

This ensures WordPress connects to Cloud SQL instead of the local MySQL instance.