Description
resource 
dbmopen ( string filename, string flags )
     The first argument is the full-path filename of the DBM file to
     be opened and the second is the file open mode which is one of
     "r", "n", "c" or "w" for read-only, new (implies read-write, and
     most likely will truncate an already-existing database of the
     same name), create (implies read-write, and will not truncate an
     already-existing database of the same name) and read-write
     respectively.
    
     Returns an identifier to be passed to the other DBM functions on
     success, or FALSE on failure.
    
     If NDBM support is used, NDBM will actually create filename.dir
     and filename.pag files. GDBM only uses one file, as does the
     internal flat-file support, and Berkeley DB creates a
     filename.db file. Note that PHP does its own
     file locking in addition to any file locking that may be done by
     the DBM library itself. PHP does not delete the
     .lck files it creates. It uses these files
     simply as fixed inodes on which to do the file locking. For more
     information on DBM files, see your Unix man pages, or obtain
     GNU's GDBM.
    
Note: When safe mode is enabled, PHP checks whether 
the files or directories you are about to operate on have the same UID (owner) as the 
script that is being executed.