I get message "There doesn't seem to be a wp-config.php file. I need this..." when running hostname/blog/wp-admin/install.php. I'm sure wp-config.php is in the hostname/blog directory.
The file_exists('../wp-config.php') doesn't seem to work unless ../ is deleted or changed into ./. In that case and after copying wp-config.php I get other errors as expected. Any idea?