prova così:

<?php
error_reporting(2047);
$nomeFile = "file.txt";
if (isset($_POST["invio"])) {
$percorso = "tmp/";
if (is_uploaded_file($_FILES['file1']['tmp_name'])) {
if (move_uploaded_file($_FILES['file1']['tmp_name'], $percorso.$nomeFile)) {

...........................
}
?>

ciao