First, make sure WordPress is set up and running with php-fpm.
A minimal Caddyfile config is:
example.com root * /var/www/wordpress php_fastcgi unix//run/php/php-version-fpm.sock file_server
Be sure to tune this config for your setup:
- Your domain name
- Site root
- The php-fpm socket or port
Be sure that WordPress is configured securely, including (but not limited to!) not allowing .php or other executable files to be uploaded by users.