Error in my PHP code _ERR[TEMP]

[bpruneau]

Someone with any experience can help me?
I receive this error:

Undefined index: TEMP in C:\blabla\www\wtf.class.content.php on line 455

... and at line 455, I have:

$oldFile = $_ENV['TEMP'].'/wtf'.$fileid.'-1';

Where do I have to define this index?

[LordShryku]

In the array $_ENV apparently....