Hooks Viewer

Security: HooksViewer only captures and logs hooks when Matomo runs in development mode ([Development] enabled = 1, or ./console development:enable). Otherwise no hook is captured, no panel is shown, nothing is logged, existing log files are deleted, and super users see a warning on every page asking to enable development mode or to uninstall the plugin.
Security: sensitive values are masked in the panel and in the log file (tokens, passwords, secrets, cookies, sessions, API keys, visitor identifiers and IPs, and the same parameters inside URLs). Set show_sensitive_values = 1 in the [HooksViewer] section of config/config.ini.php to show them.
The log files are deleted when the plugin is deactivated or uninstalled.
Removed the Openmost banners and widget.

The version number now follows the Matomo major version (5.x for Matomo 5).
Requires Matomo 5.0.0 or higher (>=5.0.0,<6.0.0-b1). The theme variables used by the argument dumps fall back to the Matomo light theme colors when they are not available (before Matomo 5.10.0).
The argument dumps follow the light or dark Matomo theme, including DarkTheme, instead of a forced dark background.
Security: the hooks are only printed into the pages of super users, as in v6. The log file still records every request.
Fix: the hooks are now gathered in one collapsible HooksViewer panel written once the response is complete, at the top of the page or of the widget, as in v6. They were printed where each hook fired, including inside the <script> holding the Matomo JS globals, which emptied piwik.token_auth and made the report widgets fail with a 401 error.
tmp/logs/hooksviewer.log is rotated to hooksviewer.log.1 above 10 MB.
README: the plugin description now shows in the Description tab of the Matomo Marketplace.

update: README.md

Major rewrite. The plugin now covers (almost) every event Matomo dispatches and renders them inline at their dispatch point.

Hook discovery

New HookCatalog scans core/ and plugins/ for every Piwik::postEvent('…') call site. Same-file self::FOO_EVENT constants are resolved automatically.
Result is cached in tmp/cache/hooksviewer-catalog.php and rebuilt whenever the source tree changes (mtime-based signature, 5 min TTL).
~258 events discovered out of the box on a clean Matomo 5 install, vs. ~210 in the previous hand-maintained list.

Rendering

Events are rendered at the moment they fire, inline in the DOM, as <details><summary>HookName</summary><pre><code>args…</code></pre></details>.
Args are pretty-printed across multiple indented lines (depth-limited, truncated at 30 entries per level / 240 chars per string), so deep arrays and objects stay readable.
Args panel is locked to a dark background with white text so it remains legible regardless of the active Matomo theme.

Safety

Inline emission is suppressed for JSON, XML, CSV, image, and tracker responses, Matomo's API and matomo.php payloads stay byte-exact.
Widget AJAX requests (format=html) keep their inline output, so hooks like ViewDataTable.filterViewDataTable, Visualization.beforeRender, Metrics.isLowerValueBetter, and Widget.filterWidgets are visible inside each widget as it loads.
Every fired hook (HTML or not) is also appended to tmp/logs/hooksviewer.log with timestamp, request id, and args. Watch with tail -f.
Activation/deactivation now flushes Matomo's merged-asset bundle so the plugin's stylesheet is picked up immediately.

Internals

One generic __call() dispatcher replaces 200+ hand-rolled stub methods. The whole plugin is ~340 lines of PHP.
Compatible with Matomo 5.x.

Initial plugin commit.

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