What kind of handler used for a dba file?

I used dba-open (http://us2.php.net/manual/en/function.dba-open.php) to create a simple database file. The linux file command tells me that the file is just "data": # file test.db test.db: data I assume this is refered to a "Constant Database" or a DB2 file. I'm able to insert, fetch, and delete entries. However I'm trying to find out exactly what kind of file this is since the documentation doesn't tell me what "default" handler it used when creating the file. thanks, -eric