Error: {"message":"ucfirst(): Argument #1 ($string) must be of type string, array given","file":"core/Plugin/ReportsProvider.php","line":37,"request_id":"9ae88","backtrace":" on core/Plugin/ReportsProvider.php(37)\n#0 core/Plugin/ReportsProvider.php(37): ucfirst(Array)\n#1 core/Http/ControllerResolver.php(101): Piwik\Plugin\ReportsProvider::factory('CoreHome', Array)\n#2 core/Http/ControllerResolver.php(59): Piwik\Http\ControllerResolver->createReportController('CoreHome', Array, Array)\n#3 core/FrontController.php(604): Piwik\Http\ControllerResolver->getController('CoreHome', Array, Array)\n#4 core/FrontController.php(168): Piwik\FrontController->doDispatch('CoreHome', Array, Array)\n#5 core/dispatch.php(32): Piwik\FrontController->dispatch()\n#6 index.php(25): require_once('c...')\n#7 {main}",

URL: https://example.yourdomain/index.php?action[%24foobar]=1

Seems in https://github.com/matomo-org/matomo/blob/4.7.0-rc2/core/FrontController.php#L462 we're not defining string. Not sure if we can change false to an empty string for $action. This might break some things. Maybe if $action is not false then we would throw an exception if $action is not a string?

Happens with PHP 8