net::ERR_CONNECTION_REFUSED, TypeError: Failed to fetch at HTMLDocument.requestItems (script.js:56:5)

I’m trying to use fetch API to get information about my database but I keep getting “net::ERR_CONNECTION_REFUSED
TypeError: Failed to fetch
at HTMLDocument.requestItems (script.js:56:5)” error

Here’s my db.php code to connect to database

    $conn=new mysqli("localhost:3306", "root", "", "online_canteen_system");
    if($conn->connect_errno){
        echo json_encode(['error'=>$conn->connect_error]);
        exit();
    }

and here’s my items.php code

 <?php 
require 'db.php';
header('Access-Control-Allow-Origin: *');  

if($_SERVER['REQUEST_METHOD']==="GET"){
    $stmt = "select name from items where status=1;";
    if($result= $_conn->query($stmt)){
        $arr= array();
        while($name= $result->fetch_assoc()['name']){
            array_push($arr,$name); 
        }
        echo json_encode(['items'=>$arr]);
    }
    else{
        echo json_encode(['error'=>'an error occured']);
    }
    exit();
}

here is the js code for the fetch api

document.addEventListener('DOMContentLoaded', requestItems);
function requestItems() {
    fetch("http://localhost:8080/backend/items.php")
        .then((res) => res.json())
        .then((data) => {
                console.log(data);
            }
        )
        .catch(err => console.log(err));
}

screenshot of error