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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 297028 $ -->
<refentry xml:id="function.sqlite-popen" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>sqlite_popen</refname>
<refpurpose>
Opens a persistent handle to an SQLite database and create the database if it does not exist
</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>resource</type><methodname>sqlite_popen</methodname>
<methodparam><type>string</type><parameter>filename</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>mode</parameter><initializer>0666</initializer></methodparam>
<methodparam choice="opt"><type>string</type><parameter role="reference">error_message</parameter></methodparam>
</methodsynopsis>
<simpara>
This function behaves identically to <function>sqlite_open</function>
except that is uses the persistent resource mechanism of PHP.
For information about the meaning of the parameters, read the
<function>sqlite_open</function> manual page.
</simpara>
<para>
<function>sqlite_popen</function> will first check to see if a persistent
handle has already been opened for the given
<parameter>filename</parameter>. If it finds one, it returns that handle
to your script, otherwise it opens a fresh handle to the database.
</para>
<para>
The benefit of this approach is that you don't incur the performance
cost of re-reading the database and index schema on each page hit served
by persistent web server SAPI's (any SAPI except for regular CGI or CLI).
</para>
<note>
<simpara>
If you use persistent handles and have the database updated by a
background process (perhaps via a crontab), and that process re-creates
the database by overwriting it (either by unlinking and rebuilding, or
moving the updated version to replace the current version),
you may experience undefined behaviour when a persistent handle on the
old version of the database is recycled.
</simpara>
<simpara>
To avoid this situation, have your background processes open the same
database file and perform their updates in a transaction.
</simpara>
</note>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>filename</parameter></term>
<listitem>
<para>
The filename of the SQLite database. If the file does not exist, SQLite
will attempt to create it. PHP must have write permissions to the file
if data is inserted, the database schema is modified or to create the
database if it does not exist.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>mode</parameter></term>
<listitem>
<para>
The mode of the file. Intended to be used to open the database in
read-only mode. Presently, this parameter is ignored by the sqlite
library. The default value for mode is the octal value
<literal>0666</literal> and this is the recommended value.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>error_message</parameter></term>
<listitem>
<para>
Passed by reference and is set to hold a descriptive error message
explaining why the database could not be opened if there was an error.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns a resource (database handle) on success, &false; on error.
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>sqlite_open</function></member>
<member><function>sqlite_close</function></member>
<member><function>sqlite_factory</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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