uploading only certain file types

[gklinux]

i'm using

$type = $_FILES['uploadedfile']['type'];
print $type;
if ($type == ... )
{
..
}
else
{
..
}

to get the file type of an uploaded file.

for text files, i get types
application/octet-stream and
test/plain

i want to limit uploading to only text files.
are there any other file types i should allow
apart from the above?

thanks,

gklinux