Do not save Array of value 0 in the database

guys, I have a form with 'n' quantities of inputs, all with the same structure:

echo "<input name='quantidade[]' type='number'>";

When I finish the form and send it to the next page, it arrives to me in array, and I use this array to save the data in a MySQL Database, I use this method to save in the database:

for( $i=0; $i<count($_POST['item']); $i++ ) {


    // insere no banco
    $PDO = db_connect();
    $sql = "INSERT INTO carrinho(quantidade) VALUES ('".$_POST['quantidade'][$i]."')";
    $stmt = $PDO->prepare( $sql );
    $stmt->bindParam( ':quantidade', $_POST['quantidade'][$i]  );

    if ($stmt->execute())
    {
        header('Location: index.php');
    }
    else
    {
        echo "Erro ao cadastrar";
        print_r($stmt->errorInfo());
    } 

}

It saves everything, and the data that has no value in the INPUT it saves with value 0, I wanted to know how do I not save the arrays with value "0".