下列常量由此扩展定义，且仅在此扩展编译入 PHP 或在运行时动态载入时可用。
DBA_LMDB_USE_SUB_DIR
(int)
LMDB Driver flag to allow the creation of a subdirectory for the database files. Available as of PHP 8.2.0.
DBA_LMDB_NO_SUB_DIR
(int)
LMDB Driver flag to disallow the creation of a subdirectory for the database files. Available as of PHP 8.2.0.