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>Database (dbm-style) abstraction layer functions</TITLE
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><DIV
CLASS="TITLEPAGE"
><H1
CLASS="title"
>XVII. Database (dbm-style) abstraction layer functions</H1
><DIV
CLASS="PARTINTRO"
><A
NAME="AEN15724"
></A
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="dba.intro"
></A
>Introduction</H1
><P
> These functions build the foundation for accessing Berkeley DB
style databases.
</P
><P
> 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
<A
HREF="http://www.sleepycat.com/"
TARGET="_top"
>Sleepycat Software's DB2</A
>.
(This is not to be confused with IBM's DB2 software, which is
supported through the <A
HREF="ref.odbc.html"
>ODBC functions</A
>.)
</P
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="dba.requirements"
></A
>Requirements</H1
><P
> The behaviour of various aspects depends on the implementation of the
underlying database. Functions such as <A
HREF="function.dba-optimize.html"
><B
CLASS="function"
>dba_optimize()</B
></A
>
and <A
HREF="function.dba-sync.html"
><B
CLASS="function"
>dba_sync()</B
></A
> will do what they promise for one
database and will do nothing for others. You have to download and install
supported dba-Handlers.
<DIV
CLASS="table"
><A
NAME="AEN15736"
></A
><P
><B
>Table 1. List of DBA handlers</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Handler</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Notes</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>dbm</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> Dbm is the oldest (original) type of Berkeley DB style
databases. You should avoid it, if possible. We do not support
the compatibility functions built into DB2 and gdbm, because
they are only compatible on the source code level, but cannot
handle the original dbm format.
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>ndbm</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> Ndbm is a newer type and more flexible than dbm. It still has
most of the arbitrary limits of dbm (therefore it is
deprecated).
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>gdbm</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> Gdbm is the <A
HREF="ftp://ftp.gnu.org/pub/gnu/gdbm/"
TARGET="_top"
>GNU database
manager</A
>.
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>db2</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> DB2 is <A
HREF="http://www.sleepycat.com/"
TARGET="_top"
>Sleepycat Software's
DB2</A
>. It is described as "a programmatic toolkit that
provides high-performance built-in database support for both
standalone and client/server applications.
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>db3</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> DB3 is <A
HREF="http://www.sleepycat.com/"
TARGET="_top"
>Sleepycat Software's
DB3</A
>.
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>db4</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> DB4 is <A
HREF="http://www.sleepycat.com/"
TARGET="_top"
>Sleepycat Software's
DB4</A
>. This is available since PHP 5.0.0.
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>cdb</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> Cdb is "a fast, reliable, lightweight package for creating and
reading constant databases." It is from the author of qmail and
can be found <A
HREF="http://cr.yp.to/cdb.html"
TARGET="_top"
>here</A
>. Since it is
constant, we support only reading operations. And since PHP 4.3.0
we support writing (not updating) through the internal cdb library.
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>cdb_make</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> Since PHP 4.3.0 we support creation (not updating) of cdb files
when the bundeled cdb library is used.
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>flatfile</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> This is available since PHP 4.3.0 for compatibility with the deprecated
<A
HREF="ref.dbm.html"
>dbm</A
> extension only and should be avoided.
However you may use this where files were created in this format. That
happens when configure could not find any external library.
</TD
></TR
></TBODY
></TABLE
></DIV
>
</P
><P
> When invoking the <A
HREF="function.dba-open.html"
><B
CLASS="function"
>dba_open()</B
></A
> or
<A
HREF="function.dba-popen.html"
><B
CLASS="function"
>dba_popen()</B
></A
> functions, one of the
handler names must be supplied as an argument. The actually
available list of handlers is displayed by invoking
<A
HREF="function.phpinfo.html"
><B
CLASS="function"
>phpinfo()</B
></A
> or <A
HREF="function.dba-handlers.html"
><B
CLASS="function"
>dba_handlers()</B
></A
>.
</P
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="dba.installation"
></A
>Installation</H1
><P
> By using the <TT
CLASS="option"
>--enable-dba=shared</TT
>
configuration option you can build a dynamic loadable modul 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
<TT
CLASS="literal"
>--with-XXXX</TT
> configure switch to your PHP configure
line.
<DIV
CLASS="table"
><A
NAME="AEN15796"
></A
><P
><B
>Table 2. Supported DBA handlers</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Handler</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Configure Switch</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>dbm</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> To enable support for dbm add
<TT
CLASS="option"
>--with-dbm[=DIR]</TT
>.
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>ndbm</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> To enable support for ndbm add
<TT
CLASS="option"
>--with-ndbm[=DIR]</TT
>.
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>gdbm</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> To enable support for gdbm add
<TT
CLASS="option"
>--with-gdbm[=DIR]</TT
>.
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>db2</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> To enable support for db2 add
<TT
CLASS="option"
>--with-db2[=DIR]</TT
>.
<DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
db2 conflicts with db3 and db4.
</P
></BLOCKQUOTE
></DIV
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>db3</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> To enable support for db3 add
<TT
CLASS="option"
>--with-db3[=DIR]</TT
>.
<DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
db3 conflicts with db2 and db4.
</P
></BLOCKQUOTE
></DIV
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>db4</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> To enable support for db4 add
<TT
CLASS="option"
>--with-db4[=DIR]</TT
>.
<DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
db4 conflicts with db2 and db3.
</P
></BLOCKQUOTE
></DIV
>
<DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
This was added in PHP 5.0.0. In earlier version you need to use
<TT
CLASS="option"
>--with-db3=DIR</TT
> with DIR being the
path to db4 librarie. It is not possible to use db versions starting
from 4.1 with PHP prior to version 4.3.0.
</P
></BLOCKQUOTE
></DIV
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>cdb</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> To enable support for cdb add
<TT
CLASS="option"
>--with-cdb[=DIR]</TT
>.
<DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
Since PHP 4.3.0 you can omit DIR to use the bundeled 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.
</P
></BLOCKQUOTE
></DIV
>
</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
><TT
CLASS="literal"
>flatfile</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
> To enable support for flatfile add
<TT
CLASS="option"
>--with-flatfile</TT
>.
<DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
This was added in PHP 4.3.0 to add compatibility with deprecated
<A
HREF="ref.dbm.html"
>dbm</A
> extension. Uee this handler only
when you cannot install one of the libraries required by the other
handlers and when you cannot use bundeled cdb handler.
</P
></BLOCKQUOTE
></DIV
>
</TD
></TR
></TBODY
></TABLE
></DIV
>
<DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
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
missconfigurations.
</P
></BLOCKQUOTE
></DIV
>
</P
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="dba.runtime"
></A
>Runtime Configuration</H1
><P
>This extension has no configuration directives defined in <TT
CLASS="filename"
>php.ini</TT
>.</P
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="dba.resources"
></A
>Resource Types</H1
><P
> The functions <A
HREF="function.dba-open.html"
><B
CLASS="function"
>dba_open()</B
></A
> and
<A
HREF="function.dba-popen.html"
><B
CLASS="function"
>dba_popen()</B
></A
> return a handle to the specified
database file to access which is used by all other dba-function calls.
</P
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="dba.constants"
></A
>Predefined Constants</H1
><P
>This extension has no constants defined.</P
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="dba.examples"
></A
>Examples</H1
><P
> <TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN15875"
></A
><P
><B
>Example 1. DBA example</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
><?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);
?></PRE
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
</P
><P
> DBA is binary safe and does not have any arbitrary limits.
However, it inherits all limits set by the underlying
database implementation.
</P
><P
> 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
<A
HREF="function.dba-open.html"
><B
CLASS="function"
>dba_open()</B
></A
> or <A
HREF="function.dba-popen.html"
><B
CLASS="function"
>dba_popen()</B
></A
>.
</P
><P
> You can access all entries of a database in a linear way by using the
<A
HREF="function.dba-firstkey.html"
><B
CLASS="function"
>dba_firstkey()</B
></A
> and <A
HREF="function.dba-nextkey.html"
><B
CLASS="function"
>dba_nextkey()</B
></A
>
functions. You may not change the database while traversing it.
</P
><P
> <TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN15886"
></A
><P
><B
>Example 2. Traversing a database</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
><?php
// ...open database...
$key = dba_firstkey ($id);
while ($key != false) {
if (...) { // remember the key to perform some action later
$handle_later[] = $key;
}
$key = dba_nextkey ($id);
}
for ($i = 0; $i < count($handle_later); $i++)
dba_delete ($handle_later[$i], $id);
?></PRE
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
</P
></DIV
></DIV
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="function.dba-close.html"
>dba_close</A
> -- Close database</DT
><DT
><A
HREF="function.dba-delete.html"
>dba_delete</A
> -- Delete entry specified by key</DT
><DT
><A
HREF="function.dba-exists.html"
>dba_exists</A
> -- Check whether key exists</DT
><DT
><A
HREF="function.dba-fetch.html"
>dba_fetch</A
> -- Fetch data specified by key</DT
><DT
><A
HREF="function.dba-firstkey.html"
>dba_firstkey</A
> -- Fetch first key</DT
><DT
><A
HREF="function.dba-handlers.html"
>dba_handlers</A
> -- List handlers available</DT
><DT
><A
HREF="function.dba-insert.html"
>dba_insert</A
> -- Insert entry</DT
><DT
><A
HREF="function.dba-list.html"
>dba_list</A
> -- List all open database files</DT
><DT
><A
HREF="function.dba-nextkey.html"
>dba_nextkey</A
> -- Fetch next key</DT
><DT
><A
HREF="function.dba-open.html"
>dba_open</A
> -- Open database</DT
><DT
><A
HREF="function.dba-optimize.html"
>dba_optimize</A
> -- Optimize database</DT
><DT
><A
HREF="function.dba-popen.html"
>dba_popen</A
> -- Open database persistently</DT
><DT
><A
HREF="function.dba-replace.html"
>dba_replace</A
> -- Replace or insert entry</DT
><DT
><A
HREF="function.dba-sync.html"
>dba_sync</A
> -- Synchronize database</DT
></DL
></DIV
></DIV
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