write the environment variables page and drop cli options

[carlos-granados]

Writes the Environment Variables reference page and removes CLI Options, which had nothing to document — the debugger has no command-line options of its own.

Six variables in alphabetical order under the PHP_DEBUGGER_ prefix: CONFIG, IGNORE, MODE, SESSION, SESSION_START, TRIGGER. Then DBGP_IDEKEY and DBGP_COOKIE, which have no renamed form, and a closing note on the XDEBUG_ prefix.

Verified against upstream/main and by running 0.3.3:

• PHP_DEBUGGER_CONFIG accepts exactly eight keys, taken from the parser rather than assumed: client_host, client_port, discover_client_host, cloud_id, idekey, log, log_level, on_demand_debugging_enabled
• PHP_DEBUGGER_IGNORE ignores the request on any value except no and 0
• PHP_DEBUGGER_SESSION_START works from the environment as well as from a request, taking its value as the session identifier; the cookie behaviour is the HTTP-only part
• DBGP_IDEKEY (debugger.c:77, called from debugger.c:882) and DBGP_COOKIE (handler_dbgp.c:2585) are both live

Also corrects a factual error on a page already published. Starting the Debugger said triggers were looked for "in the environment first, then $_GET, then $_POST, then $_COOKIE". That is backwards: xdebug_lib_find_in_globals() checks $_GET, $_POST, $_COOKIE and reaches the environment last — the source comment reads "Environment. This goes last." So a query parameter beats an environment variable of the same name.

Deleting CLI Options broke the build on all 30 routes, because the navbar's Reference link pointed at it. Repointed to /reference/settings.

[github-actions]

PR Preview Action v1.8.1
Preview removed because the pull request was closed.
2026-09-10 19:13 UTC