Undefined index notice in PHP while using MySQLi

Question

I've written this code to list data from the utenti table:

<?php 
    include("Database.php");

    $sql = "SELECT * FROM utenti";
    $rs = $conn->query($sql);

    if($rs === false){
        echo "Errore Sintassi SQL" . $conn->error;
    }else{
        $arr = $rs->fetch_all(MYSQLI_ASSOC);
    }

    foreach ($arr as $row){
        echo "<br/>";
        echo $row['id'];
        echo "<br/>";
        echo $row['nome'];
        echo "<br/>";
        echo $row['cognome'];
        echo "<br/>";
    }
?>

On my friend's computer, this works perfectly; but on my computer, I get this odd notice:

Notice: Undefined index: id in test.php on line 15

What could be causing it to fail on only one computer, and how can I fix it?

Answer 1

This could possibly stop the undefined index error.

foreach ($arr as $row) {
    foreach ($row as $value) {
        echo "<br/>";
        echo $value;
    }
}