PHP: When does the temporary uploaded files get deleted?

As soon as your PHP script finishes executing and re-saving to the defined location

Example using straight PHP, no framework

http://www.php.net/manual/en/features.file-upload.post-method.php

$uploaddir = '/var/www/uploads/';
$uploadfile = $uploaddir . basename($_FILES['userfile']['name']);

echo '<pre>';
if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile)) {
    echo "File is valid, and was successfully uploaded.\n";
} else {
    echo "Possible file upload attack!\n";
}

echo 'Here is some more debugging info:';
print_r($_FILES);

print "</pre>";

?>

If you do not do anything with them they will be deleted right after the script is finished.