PHP Core Warning – yii\base\ErrorException

$_GET = [
    'campaign' => 'newsletter',
];

$_COOKIE = [
    '_csrf' => '36a30a6134c7e0581f831904f6cb23c436289432f24ee483ee0adc6d2b43f122a:2:{i:0;s:5:"_csrf";i:1;s:32:"V2pxd1NucDBBek01dTlNckFIQ1pFbDQ1";}',
];

$_SESSION = [
    '__flash' => [],
];