dba_popen establishes a persistent database instance for path with mode using handler.
Commonly a regular path in your filesystem.
It 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.
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.
Optional string parameters which are passed to the driver.
The cdb, cdb_make, flatfile, inifile, qdbm and tcadb drivers do not support additional parameters.
The db1, db2, db3, db4, dbm, gdbm, and ndbm drivers supports a single additional parameter $filemode, which has the same meaning as the $mode parameter of chmod, and defaults to 0644.
The lmdb driver accepts two additional parameters. The first allows to specify the $filemode (see description above), and the second to specify the $mapsize, where the value should be a multiple of the page size of the OS, or zero, to use the default mapsize. The $mapsize parameter is supported as of PHP 7.3.14 and 7.4.2, respectively.
Returns a positive handle on success or false on failure.