Fatal error: Call to undefined function

[sioc]

Help: after install i get this massage:

Fatal error: Call to undefined function: ob_clean() in /mnt/kw1/08/960/00000018/htdocs/sioc-de/pictures/include/init.inc.php on line 156

but i have an other coppermine gallery running on my page: but its an older version 1.1
now i will run a new gallery for an other page an get this massage:

www.sioc.de/picures

[Nibbler]

http://coppermine-gallery.net/demo/cpg14x/docs/index.htm#what

Coppermine requires at least PHP 4.2 now.