why are images returning filesize = 0 when being uploaded?

[gjmv893]

I have a php form that uploads files, and all files work good the limit size is set at 7340032 bytes (7Mbs) and it works ok, however when I try to upload an image larger than 500kbs when I echo the values of the first if:\[code\]if(isset($_POST['upload']) && $_FILES['userfile']['size'] > 0){\[/code\]it says the image size is 0 everytime, why would this happen? the php.ini values of post_max_size is 15M and of upload_max_filesize is 10M.