prova così
codice:
<form action="upload.php" method="post" enctype="multipart/form-data">
<input type="file" name="immagine">
<input type="hidden" name="MAX_FILE_SIZE" value="10000">
<input type="submit" value="Invia il file">
</form>
upload.php
codice:
if(!isset($_FILES)) $_FILES = $HTTP_POST_FILES;
if(count($_FILES) <= 0) {
    echo "Non ci sono file in upload";
} else {
    foreach($_FILES as $key=>$file) {
          echo "Uploadato file: {$file['name']}
";
    }
}