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dba_open (PHP 3 >= 3.0.8, PHP 4, PHP 5) dba_open -- Open database Descriptionresource dba_open ( string path, string mode [, string handler [, mixed ...]] )
dba_open() establishes a database instance for
path with mode using
handler.
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.
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 webserver 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:
Table 1. 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 successfull. | | 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.
Return Values
Returns a positive handle on success, or FALSE on failure.
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dba_nextkey
