mirror of
https://github.com/sigmasternchen/php-doc-en
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885781f948
Cf. <https://github.com/php/php-src/pull/4910>. git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@348995 c90b9560-bf6c-de11-be94-00142212c4b1
253 lines
9 KiB
XML
253 lines
9 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<refentry xml:id="function.dba-open" xmlns="http://docbook.org/ns/docbook">
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<refnamediv>
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<refname>dba_open</refname>
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<refpurpose>Open database</refpurpose>
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</refnamediv>
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<refsect1 role="description">
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&reftitle.description;
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<methodsynopsis>
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<type>resource</type><methodname>dba_open</methodname>
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<methodparam><type>string</type><parameter>path</parameter></methodparam>
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<methodparam><type>string</type><parameter>mode</parameter></methodparam>
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<methodparam choice="opt"><type>string</type><parameter>handler</parameter></methodparam>
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<methodparam choice="opt"><type>string</type><parameter>...</parameter></methodparam>
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</methodsynopsis>
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<para>
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<function>dba_open</function> establishes a database instance for
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<parameter>path</parameter> with <parameter>mode</parameter> using
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<parameter>handler</parameter>.
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</para>
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</refsect1>
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<refsect1 role="parameters">
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&reftitle.parameters;
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<para>
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<variablelist>
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<varlistentry>
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<term><parameter>path</parameter></term>
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<listitem>
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<para>
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Commonly a regular path in your filesystem.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>mode</parameter></term>
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<listitem>
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<para>
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It is <literal>r</literal> for read access, <literal>w</literal> for
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read/write access to an already existing database, <literal>c</literal>
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for read/write access and database creation if it doesn't currently exist,
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and <literal>n</literal> for create, truncate and read/write access.
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The database is created in BTree mode, other modes (like Hash or Queue)
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are not supported.
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</para>
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<para>
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Additionally you can set the database lock method with the next char.
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Use <literal>l</literal> to lock the database with a <filename>.lck</filename>
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file or <literal>d</literal> to lock the databasefile itself. It is
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important that all of your applications do this consistently.
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</para>
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<para>
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If you want to test the access and do not want to wait for the lock
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you can add <literal>t</literal> as third character. When you are
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absolutely sure that you do not require database locking you can do
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so by using <literal>-</literal> instead of <literal>l</literal> or
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<literal>d</literal>. When none of <literal>d</literal>,
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<literal>l</literal> or <literal>-</literal> is used, dba will lock
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on the database file as it would with <literal>d</literal>.
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</para>
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<note>
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<para>
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There can only be one writer for one database file. When you use dba on
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a web server and more than one request requires write operations they can
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only be done one after another. Also read during write is not allowed.
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The dba extension uses locks to prevent this. See the following table:
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<table>
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<title>DBA locking</title>
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<tgroup cols="9">
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<thead>
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<row>
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<entry>already open</entry>
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<entry><parameter>mode</parameter> = "rl"</entry>
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<entry><parameter>mode</parameter> = "rlt"</entry>
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<entry><parameter>mode</parameter> = "wl"</entry>
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<entry><parameter>mode</parameter> = "wlt"</entry>
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<entry><parameter>mode</parameter> = "rd"</entry>
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<entry><parameter>mode</parameter> = "rdt"</entry>
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<entry><parameter>mode</parameter> = "wd"</entry>
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<entry><parameter>mode</parameter> = "wdt"</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>not open</entry>
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<entry>ok</entry>
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<entry>ok</entry>
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<entry>ok</entry>
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<entry>ok</entry>
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<entry>ok</entry>
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<entry>ok</entry>
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<entry>ok</entry>
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<entry>ok</entry>
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</row>
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<row>
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<entry><parameter>mode</parameter> = "rl"</entry>
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<entry>ok</entry>
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<entry>ok</entry>
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<entry>wait</entry>
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<entry>false</entry>
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<entry>illegal</entry>
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<entry>illegal</entry>
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<entry>illegal</entry>
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<entry>illegal</entry>
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</row>
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<row>
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<entry><parameter>mode</parameter> = "wl"</entry>
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<entry>wait</entry>
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<entry>false</entry>
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<entry>wait</entry>
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<entry>false</entry>
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<entry>illegal</entry>
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<entry>illegal</entry>
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<entry>illegal</entry>
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<entry>illegal</entry>
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</row>
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<row>
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<entry><parameter>mode</parameter> = "rd"</entry>
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<entry>illegal</entry>
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<entry>illegal</entry>
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<entry>illegal</entry>
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<entry>illegal</entry>
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<entry>ok</entry>
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<entry>ok</entry>
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<entry>wait</entry>
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<entry>false</entry>
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</row>
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<row>
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<entry><parameter>mode</parameter> = "wd"</entry>
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<entry>illegal</entry>
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<entry>illegal</entry>
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<entry>illegal</entry>
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<entry>illegal</entry>
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<entry>wait</entry>
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<entry>false</entry>
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<entry>wait</entry>
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<entry>false</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<simplelist>
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<member>ok: the second call will be successfull.</member>
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<member>wait: the second call waits until <function>dba_close</function> is called for the first.</member>
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<member>false: the second call returns false.</member>
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<member>illegal: you must not mix <literal>"l"</literal> and <literal>"d"</literal> modifiers for <parameter>mode</parameter> parameter.</member>
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</simplelist>
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</para>
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</note>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>handler</parameter></term>
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<listitem>
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<para>
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The name of the <link linkend="dba.requirements">handler</link> which
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shall be used for accessing <parameter>path</parameter>. It is passed
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all optional parameters given to <function>dba_open</function> and
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can act on behalf of them.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>...</parameter></term>
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<listitem>
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<para>
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Optional &string; parameters which are passed to the driver.
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</para>
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<para>
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The <literal>cdb</literal>, <literal>cdb_make</literal>, <literal>flatfile</literal>,
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<literal>inifile</literal>, <literal>qdbm</literal> and <literal>tcadb</literal> drivers
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do not support additional parameters.
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</para>
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<para>
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The <literal>db1</literal>, <literal>db2</literal>, <literal>db3</literal>,
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<literal>db4</literal>, <literal>dbm</literal>, <literal>gdbm</literal>,
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and <literal>ndbm</literal> drivers supports a single additional parameter <literal>$filemode</literal>,
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which has the same meaning as the <literal>$mode</literal> parameter of <function>chmod</function>,
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and defaults to <literal>0644</literal>.
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</para>
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<para>
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The <literal>lmdb</literal> driver accepts two additional parameters. The first
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allows to specify the <literal>$filemode</literal> (see description above), and the
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second to specify the <literal>$mapsize</literal>, where the value should be a multiple
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of the page size of the OS, or zero, to use the default mapsize. The <literal>$mapsize</literal>
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parameter is supported as of PHP 7.3.14 and 7.4.2, respectively.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect1>
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<refsect1 role="returnvalues">
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&reftitle.returnvalues;
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<para>
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Returns a positive handle on success&return.falseforfailure;.
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</para>
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</refsect1>
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<refsect1 role="changelog">
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&reftitle.changelog;
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<informaltable>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>&Version;</entry>
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<entry>&Description;</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>7.3.14, 7.4.2</entry>
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<entry>
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The <literal>lmdb</literal> driver now supports an additional <literal>$mapsize</literal>
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parameter.
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</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</refsect1>
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<refsect1 role="seealso">
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&reftitle.seealso;
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<para>
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<simplelist>
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<member><function>dba_popen</function></member>
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<member><function>dba_close</function></member>
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</simplelist>
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</para>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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