$_FILES['']['size'] - does PHP check file size on server side?

when a file is uploaded using a PHP script, which is the best way to check file size?

$_FILES['']['size'] OR filesize()?

the value in $_FILES['']['size'] - does PHP check the file size in the server, or is it the value sent by the browser while uploading the file?

$_FILES['']['type'] - is the value sent by the browser, and has a security problem while uploading the file. is $_FILES['']['size'] like this?

you have the manual here

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

size is the actual size of the file on the server