File uploads in PHP

My PHP script needs to receive some files. I've seen sites which accept them; they have a Browse button which lets the user select a file to send. That's what I want to do. I have a few questions about this. First of all, this is with php4.06. Secondly, the files are all going to be images, and not very large: no more than 50k. What's the best way to do this? I notice that PHP can store these files on disk, but I'm going to be storing them in a DB. I would rather receive them directly into a PHP variable. Is this possible? Or should I take them in a file, and then read them back in to a variable? Also, if they need to go into a file, which directory is safest for this? /tmp contains some important files. And finally, how do I limit the maximum file size that PHP will accept? Thanks