仅向会话数组添加整数

Question

So I have problem where I am using AJAX + PHP to insert product id to $SESSION['korpica'] = array(); Everything is working for id where i have only numbers(222,223,440,900,911) but when it comes to (A320M BAZOOKA, A320M GAMING PRO, A320M PRO-VH PLUS) it is not working. I searched but nothing helped me. Here is my code .

Declaring array in index.php

session_start();
$korpa = array();
$_SESSION['korpica'] = $korpa;

button

<button type="button" class="addToCart btn-button" title="Dodaj u korpu" onclick="dodaj('<?php echo $sifra; ?>');">  <i class="fa fa-shopping-basket"></i>
<span>Add to Cart</span>   
</button>

dodaj.js

function dodaj(sifra) {
    $.ajax({
        url: 'dodajUKorpu.php',
        type: "GET",
        data: {'korpas':sifra}


    });
}

dodajUKorpu.php

<?php session_start(); ?>
<?php
if(isset($_GET['korpas']) && $_GET['korpas']!=0){
    array_push($_SESSION['korpica'], $_GET['korpas']);
}

?>

Working for id -> 222, 223, 444, 900, 121, 911

Not working for id -> A320M BAZOOKA, A320M GAMING PRO, A320M PRO-VH PLUS, A68HM-P33 V1, AD5150JAHMBOX