NGINX 1.30 makes upstream HTTP/1.1 keep-alive the default. Here is how to audit backends, clean inherited config, and upgrade without avoidable surprises.
Use `defined()` first, `constant()` only when you need a dynamic lookup, and `get_defined_constants(true)` for audits. This updated PHP and WordPress guide explains the safe pattern for `DISALLOW_FILE_EDIT` and environment troubleshooting.