This was the thread we had the discussion about: http://www.devfuse.c...em-global-hook/
Does other php code work in the same place? Maybe try wrapping in php tags.
<?php require_once( IPSLib::getAppDir( 'videos' ) . "/sources/functions.php" ); $this->registry->setClass('video_functions', new classVideos( $this->registry ) ); print $this->registry->getClass('video_functions')->global_block(); ?>