Sure... PHP recognizes Windows drive letters, so just open a path where there is more space, such as:
$fp = fopen('D:/backup/bigFile.txt');
fwrite($fp, $LargeAmountOfData . $MoreAndMoreData . $etc);
fclose($fp);
EDIT: PHP also recognizes UNC paths (I believe), so you could even dump the data to a different server:
$fp = fopen('\\\\FileServer1\\c$\\Webserver_backup\\\bigFile.txt');
fwrite($fp, $LargeAmountOfData . $MoreAndMoreData . $etc);
fclose($fp);