php say some results aren't undifined while some are

I have a wierd php problem. I get data from mysql with code below

SELECT kitap.kit_id, kitap.kit_adi, yazar.yad as yazar,  
        yayinevi.yeviad as yayinevi,kitap.isbn,kitap.basim_yili, 
        kitap.baski_no,kitap.dil,kitap.cilt,kitap.sayfa, 
        kitap.kategori,kitap.durum
FROM kitap 
    INNER JOIN kitapyayinevi ON kitap.kit_id = kitapyayinevi.kit_id 
    INNER JOIN kitapyazar ON kitap.kit_id = kitapyazar.kit_id 
    INNER JOIN yayinevi ON kitapyayinevi.yevi_id = yayinevi.yevi_id 
    INNER JOIN yazar ON kitapyazar.yazar_id = yazar.yazar_id
SQL;

    $stmt = $connection->query($sql);
    $result = $stmt->fetchAll(PDO::FETCH_ASSOC);
    var_dump($result); //This is for debugging purposes

But when I try to print them with code below;

<?php foreach ($result as $item): ?>
    <tr>
        <td class="hide"><?= $item->kit_id; ?></td>
        <td><?= $item->kit_adi; ?></td>
        <td><?= $item->yazar; ?></td>
        <td><?= $item->yayinevi; ?></td>
        <td><?= $item->isbn; ?></td>
        <td><?= $item->baski_no; ?></td>
        <td><?= $item->basim_yili; ?></td>
        <td><?= $item->dil; ?></td>
        <td><?= $item->cilt; ?></td>
        <td><?= $item->sayfa; ?></td>
        <td><?= $item->kategori; ?></td>

It gives me the error below. Everything except $item->yazar and $item->yayinevi print out just fine;

Notice: Undefined property: stdClass::$yazar in C:\Users\Nihal\Documents\KutuphaneYonetim\php\body.php on line 38

Notice: Undefined property: stdClass::$yayinevi in C:\Users\Nihal\Documents\KutuphaneYonetim\php\body.php on line 39

And var_dump($result) prints out like this;

array(1) { [0]=> array(12) { 
                ["kit_id"]=> string(2) "25" 
                ["kit_adi"]=> string(7) "Sınır" 
                ["yazar"]=> string(13) "Beyza Alkoç " 
                ["yayinevi"]=> string(15) "İNDİGO KİTAP" 
                ["isbn"]=> string(10) "6052361580" 
                ["basim_yili"]=> string(4) "2018" 
                ["baski_no"]=> string(1) "4" 
                ["dil"]=> string(8) "TÜRKÇE" 
                ["cilt"]=> string(12) "Karton Kapak" 
                ["sayfa"]=> string(3) "400" 
                ["kategori"]=> string(5) "Roman" 
                ["durum"]=> string(5) "rafta" 
                } 
        }

What would be the problem? can you guys help me find?