var_export does not handle circular references

[anuj9196]

Addding this line to my controller

public $components = [
    'RequestHandler' => [
        'viewClassMap' => ['csv' => 'CsvView.Csv']
    ]
];

is giving error as

var_export does not handle circular references

Context is

$name = 'RequestHandler'
$config = [
	'viewClassMap' => [
		'csv' => 'CsvView.Csv'
	]
]
$existing = object(Cake\Controller\Component\RequestHandlerComponent) {

	'components' => [],
	'implementedEvents' => [
		'Controller.startup' => 'startup',
		'Controller.beforeRender' => 'beforeRender',
		'Controller.beforeRedirect' => 'beforeRedirect'
	],
	'_config' => [
		'checkHttpCache' => true,
		'viewClassMap' => [
			[maximum depth reached]
		],
		'inputTypeMap' => [
			[maximum depth reached]
		],
		'enableBeforeRedirect' => true
	]

}
$msg = 'The "RequestHandler" alias has already been loaded with the following config: '
$hasConfig = true
$existingConfig = [
	'checkHttpCache' => true,
	'viewClassMap' => [
		'json' => 'Json',
		'xml' => 'Xml',
		'ajax' => 'Ajax'
	],
	'inputTypeMap' => [
		'json' => [
			(int) 0 => 'json_decode',
			(int) 1 => true
		],
		'xml' => [
			(int) 0 => [
				[maximum depth reached]
			]
		]
	],
	'enableBeforeRedirect' => true
]
$fail = true
$value = [
	'csv' => 'CsvView.Csv'
]
$key = 'viewClassMap'

[josegonzalez]

We don't call var_export within this plugin. Is there a place in your codebase or maybe a stacktrace for this error?

[isemantics]

I'm not sure why it happens, but I got the same message. The following information might help you guys. Ofcourse this is just my situation that (maybe) happens to include Crud and CakePHP together ( this might also happen without Crud, who knows at the moment ).

My situation: Build API's before, but wanted to build something real quick without my normal code/overhead (so: just a demo). I was following the steps from: How to build a CakePHP3 API in minutes. My code is mostly equal to that ( I know this does not include my small changes, which might give the error and also some updates to CakePHP3 and other packages after the tutorial was written ( because some things needed to be fixed to run @cakephp 3.6).
Also: I have App ( normal classes and folders for Controller etc. ), but also have an Api prefix, with /src/Controller/Api/AppController.php being the main class ( not extending from src/Controller/AppController but from Cake's Controller class ). The prefix works and I do get results for /api/quotes/index.json (among others).

Anyway; some stuff:

1. I got this message (it seems, from a different source than the OP):
   Warning (2): var_export does not handle circular references [CORE/src/Core/ObjectRegistry.php, line 147]
   Which shows where it comes from (in my case), namely: "ObjectRegistry" from CakePHP itself (not CRUD). Thus, this probably explains why @josegonzalez said "we don't call var_export in this plugin". It must come from some combination of things that eventually hits the wrong note in ObjectRegistry
2. Stacktrace:

var_export - [internal], line ??
Cake\Core\ObjectRegistry::_checkDuplicate() - CORE/src/Core/ObjectRegistry.php, line 147
Cake\Core\ObjectRegistry::load() - CORE/src/Core/ObjectRegistry.php, line 86
Cake\Controller\Controller::loadComponent() - CORE/src/Controller/Controller.php, line 334
Cake\Controller\Controller::_loadComponents() - CORE/src/Controller/Controller.php, line 642
Cake\Controller\Controller::__construct() - CORE/src/Controller/Controller.php, line 275
Cake\Error\ExceptionRenderer::_getController() - CORE/src/Error/ExceptionRenderer.php, line 126
Cake\Error\ExceptionRenderer::__construct() - CORE/src/Error/ExceptionRenderer.php, line 91
Cake\Error\Middleware\ErrorHandlerMiddleware::getRenderer() - CORE/src/Error/Middleware/ErrorHandlerMiddleware.php, line 174
Cake\Error\Middleware\ErrorHandlerMiddleware::handleException() - CORE/src/Error/Middleware/ErrorHandlerMiddleware.php, line 116
Cake\Error\Middleware\ErrorHandlerMiddleware::__invoke() - CORE/src/Error/Middleware/ErrorHandlerMiddleware.php, line 100
Cake\Http\Runner::__invoke() - CORE/src/Http/Runner.php, line 65
Cake\Http\Runner::run() - CORE/src/Http/Runner.php, line 51
Cake\Http\Server::run() - CORE/src/Http/Server.php, line 98
[main] - ROOT/webroot/index.php, line 40

It shows it hits loadComponents() so it might reflect an error in the component config/load. This is the context (from the stacktrace/error):

$name = 'RequestHandler'
$config = [
	'enableBeforeRedirect' => true
]
$existing = object(Cake\Controller\Component\RequestHandlerComponent) {

	'components' => [],
	'implementedEvents' => [
		'Controller.startup' => 'startup',
		'Controller.beforeRender' => 'beforeRender',
		'Controller.beforeRedirect' => 'beforeRedirect'
	],
	'_config' => [
		'checkHttpCache' => true,
		'viewClassMap' => [
			[maximum depth reached]
		],
		'inputTypeMap' => [
			[maximum depth reached]
		],
		'enableBeforeRedirect' => false
	]

}
$msg = 'The "RequestHandler" alias has already been loaded with the following config: '
$hasConfig = true
$existingConfig = [
	'checkHttpCache' => true,
	'viewClassMap' => [
		'json' => 'Json',
		'xml' => 'Xml',
		'ajax' => 'Ajax'
	],
	'inputTypeMap' => [
		'json' => [
			(int) 0 => 'json_decode',
			(int) 1 => true
		],
		'xml' => [
			(int) 0 => [
				[maximum depth reached]
			]
		]
	],
	'enableBeforeRedirect' => false
]
$fail = true
$value = true
$key = 'enableBeforeRedirect'

Which shows "RequestHandler already loaded" in $msg (as it did in the OP's post).
Debugging and checking a little more, I've found that there seems to be a difference in loading via $components = ['RequestHandler' => ['enableBeforeRedirect' => true]] and loading via loadComponent() in the main /src/Controller/AppController::initialize() .

So; writing this comment solved my problem it seems. All var_export messages disappear when I remove the $components version in AppController and replace it with the initialize() version ( in the same class, no other changes ). That works.

Might help OP in his situation ( even though this is a year old issue ).

Conclusion: Don't think it's a CRUD/csvview issue, probably just wrong configuration in the main app/routing.

[josegonzalez]

Thanks for the update!