If in the php.ini "post_max_size" is set to 0, there is no limitation in the post size:
[from php.ini]
; Maximum size of POST data that PHP will accept.
; Its value may be 0 to disable the limit. It is ignored if POST data reading
; is disabled through enable_post_data_reading.
; http://php.net/post-max-size
post_max_size = 0

However, in this case, the validator (tested via Form) trigger always
"The uploaded file was too large. Please try to upload a smaller file."

[Fix]
Enable the control only if post_max_size > 0