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.
注: 當安全模式開啟,PHP會檢查執行的腳本和 要操作的檔案或目錄是否有相同的UID(擁有者)。