Requirements

• Go 1.26 or newer.
• A host running PHP-FPM. The library shells out to the php-fpm binary for -tt (parse the effective configuration) and -t (validate one), scans /proc to find masters, and signals them. It runs where php-fpm runs, which in practice means Linux. On other platforms the process scan and the trust checks degrade rather than pretend.
• The right user for what you are doing. Discovery reads other processes' details, and before it executes or signals anything it checks that the binary and config are owned by root or by the calling process. Running as root reads everything and applies the strict directory-ownership checks; running as the php-fpm user reads its own master; running as a stranger sees less, on purpose. See Identity and trust.

The library holds no long-running state and starts no goroutines of its own beyond the lifetime of a single call. Its only caches are the parsed configuration (per binary+config pair) and the PHP version/extension lookup; both are process-lifetime and the first must be invalidated when you change a configuration — see The configuration cache.