dba_popen() establishes a persistent database instance for path with mode using handler.
path is commonly a regular path in your filesystem.
mode is "r" for read access, "w" for read/write access to an already existing database, "c" for read/write access and database creation if it doesn't currently exist, and "n" for create, truncate and read/write access.
handler is the name of the handler which shall be used for accessing path. It is passed all optional parameters given to dba_popen() and can act on behalf of them.
dba_popen() returns a positive handle or FALSE, in the case the open is successful or fails, respectively.