PHP Core Warning – yii\base\ErrorException

$_GET = [
    'cat-ref' => 'pediatria',
];

$_COOKIE = [
    '_csrf' => '3ec02aaff19fdd8a653fd422ed94d09e76e0d1b8923683d992af752bcc1f91f6a:2:{i:0;s:5:"_csrf";i:1;s:32:"eHFNV0RkNWl3RFAyWlFSYXJ2OFB1YWNa";}',
    'identity-fe' => '74e39dhah96gjen337bq28jf61',
];

$_SESSION = [
    '__flash' => [],
    '__returnUrl' => '/ricerca/i-nostri-ricercatori/elena-daveri',
];