[TYPO3] http post files returns error: 4 after looking at debug - how do I find out what those errors are and where they are?

[dave typo]

when I type

debug($GLOBALS["HTTP_POST_FILES"]);


within an if statement, I get a return output that says:


userfile	
            name	
            type	
            tmp_name	
            error	         4
            size	         0



so my question is, how do I find out what those four errors are, or
where they are? a single numbered output doesn't really tell me much..



thanks for your help.

-dave