(PHP 4, PHP 5, PHP 7, PHP 8)
dba_open — Open database
$path
,$mode
,$handler
= null
,$permission
= 0644,$map_size
= 0,$flags
= null
dba_open() establishes a database instance for
path
with mode
using
handler
.
path
Commonly a regular path in your filesystem.
mode
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 database is created in BTree mode, other modes (like Hash or Queue)
are not supported.
Additionally you can set the database lock method with the next char.
Use l
to lock the database with a .lck
file or d
to lock the databasefile itself. It is
important that all of your applications do this consistently.
If you want to test the access and do not want to wait for the lock
you can add t
as third character. When you are
absolutely sure that you do not require database locking you can do
so by using -
instead of l
or
d
. When none of d
,
l
or -
is used, dba will lock
on the database file as it would with d
.
Note:
There can only be one writer for one database file. When you use dba on a web server and more than one request requires write operations they can only be done one after another. Also read during write is not allowed. The dba extension uses locks to prevent this. See the following table:
DBA locking already open mode
= "rl"mode
= "rlt"mode
= "wl"mode
= "wlt"mode
= "rd"mode
= "rdt"mode
= "wd"mode
= "wdt"not open ok ok ok ok ok ok ok ok mode
= "rl"ok ok wait false illegal illegal illegal illegal mode
= "wl"wait false wait false illegal illegal illegal illegal mode
= "rd"illegal illegal illegal illegal ok ok wait false mode
= "wd"illegal illegal illegal illegal wait false wait false
- ok: the second call will be successful.
- wait: the second call waits until dba_close() is called for the first.
- false: the second call returns false.
- illegal: you must not mix
"l"
and"d"
modifiers formode
parameter.
handler
The name of the handler which
shall be used for accessing path
. It is passed
all optional parameters given to dba_open() and
can act on behalf of them. If handler
is null
,
then the default handler is invoked.
permission
Optional int parameter which is passed to the driver. It has the same meaning as
the permissions
parameter of chmod(),
and defaults to 0644
.
The db1
, db2
, db3
,
db4
, dbm
, gdbm
,
ndbm
, and lmdb
drivers support the
permission
parameter.
map_size
Optional int parameter which is passed to the driver. Its value should be a multiple of the page size of the OS, or zero, to use the default map size.
Only the lmdb
driver accepts the map_size
parameter.
flags
Flags to pass to the database drivers. If null
the default flags will be provided.
Currently, only the LMDB driver supports the following flags
DBA_LMDB_USE_SUB_DIR
and
DBA_LMDB_NO_SUB_DIR
.
Returns a positive handle on success or false
on failure.
false
is returned and an E_WARNING
level error is issued when
handler
is null
, but there is no default handler.
Version | Description |
---|---|
8.2.0 |
flags is added.
|
8.2.0 |
handler is now nullable.
|
7.3.14, 7.4.2 |
The lmdb driver now supports an additional map_size
parameter.
|