PHP Core Warning – yii\base\ErrorException

$_GET = [
    'ancestorsSlug' => 'magazine',
    'slug' => 'risultati-ricerca-magazine',
    'modelClass' => 'ymool\\base\\Page',
    'q' => 'molluschi',
    'search' => '1',
];

$_SESSION = [
    '__flash' => [],
    '__returnUrl' => '/magazine/risultati-ricerca-magazine?q=molluschi&search=1',
];