how can I improve the check name file part
I have two minor comments.

First, I prefer having my variables defined in all branches, to avoid the PHP Notice:  Undefined variable:... error in logs. So, an initialization

$isMove = false;


would be nice. Btw, maybe $isMoved seems a bit more accurate/correct name. This part might also be written like this:

if (!is_uploaded_file($_FILES['file']['tmp_name'])) return false;
$safe_filename = $dateadded . preg_replace(array('/\s+/', '/[^-\.\w]+/'), array('_', ''), trim($_FILES['file']['name']));
if ($_FILES['file']['size'] &gt; $MAXIMUM_FILESIZE) return false;
if (!preg_match($rEFileTypes, strrchr($safe_filename, '.'))) return false;
if (!move_uploaded_file($_FILES['file']['tmp_name'], $dir_base . $safe_filename)) return false;
return $safe_filename;


Depending on your taste, this might be easier to read.

My second comment is related to this:

$rEFileTypes = "/^\.($filetype){1}$/i";


What is the purpose of {1} (which means "repeat once")? I'd write that regex like this:

$rEFileTypes = "/\.($filetype)\$/i";


and I would replace

preg_match($rEFileTypes, strrchr($safe_filename, '.'))


with

preg_match($rEFileTypes, $safe_filename)


It seems to me a bit less cluttered this way, and I'd expect such regex to be faster than doing the old one + strrchr, but I have no proof that it really is. However, I don't think this is a kind of code in which speed is very important (upload of a file and moving it around will eat up much more time).

Btw, $filetypes might be a bit better name.

A bit more important comment is regarding the possibility that, given a long enough filename, your safe one will grow too long when you prepend it with a date, and you will lose the file extension (or a part of it). You might want to address that issue by checking the length and trimming the filename part if needed.

Now, for the general approach, there is a question about what you're doing with this. Usually, it is better to keep the original filenames in a database, and to store the uploaded files under a completely generic name (using, for example, an auto_increment primary key from the filenames table). Also, if you don't need filenames at all, you can then just make them generic.

Notice that your $dateadded makes it very likely that your filenames are unique, but it doesn't really guarantee it. Depending on your use and the expected number of users, this might be a potential problem (although I wouldn't expect it).