Description
Dba\Connectionfalse dba_open(
string $path
,
string $mode
,
stringnull $handler
= null
,
int $permission
= 0644,
int $map_size
= 0,
intnull $flags
= null
)
Parameters
-
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 for mode
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
.
Return Values
Returns a Dba\Connection instance on success or false
on failure.
Errors/Exceptions
false
is returned and an E_WARNING
level error is issued when
handler
is null
, but there is no default handler.