These functions build the foundation for accessing Berkeley DB style databases.
This is a general abstraction layer for several file-based databases. As such, functionality is limited to a common subset of features supported by modern databases such as » Sleepycat Software's DB2. (This is not to be confused with IBM's DB2 software, which is supported through the ODBC functions.)
The behaviour of various aspects depends on the implementation of the underlying database. Functions such as dba_optimize() and dba_sync() will do what they promise for one database and will do nothing for others. You have to download and install supported dba-Handlers.
When invoking the dba_open() or dba_popen() functions, one of the handler names must be supplied as an argument. The actually available list of handlers is displayed by invoking phpinfo() or dba_handlers().
By using the --enable-dba=shared configuration option you can build a dynamic loadable module to enable PHP for basic support of dbm-style databases. You also have to add support for at least one of the following handlers by specifying the --with-XXXX configure switch to your PHP configure line.
After configuring and compiling PHP you must execute the following test from commandline: php run-tests.php ext/dba. This shows whether your combination of handlers works. Most problematic are dbm and ndbm which conflict with many installations. The reason for this is that on several systems these libraries are part of more than one other library. The configuration test only prevents you from configuring malfunctioning single handlers but not combinations.
To enable support for dbm add --with-dbm[=DIR].
Note: dbm normally is a wrapper which often results in failures. This means you should only use dbm if you are sure it works and if you really need this format.
To enable support for ndbm add --with-ndbm[=DIR].
Note: ndbm normally is a wrapper which often results in failures. This means you should only use ndbm if you are sure it works and if you really need this format.
To enable support for db2 add --with-db2[=DIR].
Note: db2 conflicts with db3 and db4.
To enable support for db3 add --with-db3[=DIR].
Note: db3 conflicts with db2 and db4.
To enable support for db4 add --with-db4[=DIR].
Note: db4 conflicts with db2 and db3.
Note: This was added in PHP 4.3.2. In earlier versions of PHP you need to use --with-db3=DIR with DIR being the path to db4 library. It is not possible to use db versions starting from 4.1 with PHP prior to version 4.3.0. Also, the db libraries with versions 4.1 through 4.1.24 cannot be used in any PHP version.
To enable support for cdb add --with-cdb[=DIR].
Note: Since PHP 4.3.0 you can omit DIR to use the bundled cdb library that adds the cdb_make handler which allows creation of cdb files and allows to access cdb files on the network using PHP's streams.
To enable support for flatfile add --with-flatfile.
Note: This was added in PHP 4.3.0 to add compatibility with deprecated dbm extension. Use this handler only when you cannot install one of the libraries required by the other handlers and when you cannot use bundled cdb handler.
To enable support for inifile add --with-inifile.
Note: This was added in PHP 5.0.0 and allows to read and set microsoft style .ini files (like the php.ini file).
To enable support for qdbm add --with-qdbm[=DIR].
Note: qdbm conflicts with dbm and gdbm.
Note: This was added in PHP 5.0.0. The qdbm library can be loaded from » http://qdbm.sourceforge.net.
Note: Up to PHP 4.3.0 you are able to add both db2 and db3 handler but only one of them can be used internally. That means that you cannot have both file formats. Starting with PHP 5.0.0 there is a configuration check avoid such misconfigurations.
This extension has no configuration directives defined in php.ini.
The functions dba_open() and dba_popen() return a handle to the specified database file to access which is used by all other dba-function calls.
This extension has no constants defined.
Example#1 DBA example
<?php$id = dba_open("/tmp/test.db", "n", "db2");if (!$id) { echo "dba_open failed\n"; exit;}dba_replace("key", "This is an example!", $id);if (dba_exists("key", $id)) { echo dba_fetch("key", $id); dba_delete("key", $id);}dba_close($id);?>
DBA is binary safe and does not have any arbitrary limits. However, it inherits all limits set by the underlying database implementation.
All file-based databases must provide a way of setting the file mode of a new created database, if that is possible at all. The file mode is commonly passed as the fourth argument to dba_open() or dba_popen().
You can access all entries of a database in a linear way by using the dba_firstkey() and dba_nextkey() functions. You may not change the database while traversing it.
Example#2 Traversing a database
<?php// ...open database...$key = dba_firstkey($id);while ($key != false) { if (true) { // remember the key to perform some action later $handle_later[] = $key; } $key = dba_nextkey($id);}foreach ($handle_later as $val) { dba_delete($val, $id);}?>
