How to split file for import

Question

I have a file that has no data separation and I need to insert it in the database, how can I import it.

For example, the file is like this:

931398401312 

I want to divide it into 4 columns, example:

|column1|column2|column3|column4|
|931    |3984   |01     |312    |

My code:

$arquivo_tmp = $_FILES['arquivo']['tmp_name'];

$dados = file($arquivo_tmp);

foreach($dados as $linha){
    $linha = trim($linha);
    $valor = explode(',', $linha);
    var_dump($valor);

    $column1 = $valor[0];
    $column2 = $valor[1];
    $column3 = $valor[2];
    $column4 = $valor[3];

    $result_usuario = "INSERT INTO teste (column1, column2, column3, column4) VALUES ('$column1', '$column2', '$column3', '$column4')";

    $resultado_usuario = mysqli_query($conn, $result_usuario);  
}