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<?xml version="1.0" encoding="utf-8"?>
<refentry xml:id="pdo-sqlite.createfunction" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<refnamediv>
<refname>Pdo\Sqlite::createFunction</refname>
<refpurpose>
Registers a user-defined function for use in SQL statements
</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis role="Pdo\\Sqlite">
<modifier>public</modifier> <type>bool</type><methodname>Pdo\Sqlite::createFunction</methodname>
<methodparam><type>string</type><parameter>function_name</parameter></methodparam>
<methodparam><type>callable</type><parameter>callback</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>num_args</parameter><initializer>-1</initializer></methodparam>
<methodparam choice="opt"><type>int</type><parameter>flags</parameter><initializer>0</initializer></methodparam>
</methodsynopsis>
<simpara>
This method allows PHP function to be registered with SQLite as a
user-defined function, so that it can be called within SQL queries.
The defined function can be used in any SQL query that allows function calls,
for example <literal>SELECT</literal>, <literal>UPDATE</literal>, or triggers.
</simpara>
<tip>
<simpara>
By using this method it is possible to override native SQL functions.
</simpara>
</tip>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<variablelist>
<varlistentry>
<term><parameter>function_name</parameter></term>
<listitem>
<simpara>
The name of the function used in SQL statements.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>callback</parameter></term>
<listitem>
<simpara>
Callback function to handle the defined SQL function.
</simpara>
<note>
<simpara>
Callback functions should return a type understood by SQLite (i.e.
<link linkend="language.types.intro">scalar type</link>).
</simpara>
</note>
<para>
This function need to be defined as:
<methodsynopsis>
<type>mixed</type><methodname><replaceable>callback</replaceable></methodname>
<methodparam><type>mixed</type><parameter>value</parameter></methodparam>
<methodparam rep="repeat"><type>mixed</type><parameter>values</parameter></methodparam>
</methodsynopsis>
<variablelist>
<varlistentry>
<term><parameter>value</parameter></term>
<listitem>
<para>
The first argument passed to the SQL function.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>values</parameter></term>
<listitem>
<para>
Further arguments passed to the SQL function.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>num_args</parameter></term>
<listitem>
<simpara>
The number of arguments that the SQL function takes.
If this parameter is <literal>-1</literal>,
then the SQL function may take any number of arguments.
</simpara>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>flags</parameter></term>
<listitem>
<simpara>
A bitmask of flags.
Currently, only <constant>Pdo\Sqlite::DETERMINISTIC</constant> is supported,
which specifies that the function always returns the same result given
the same inputs within a single SQL statement.
</simpara>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<simpara>
&return.success;
</simpara>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<example xml:id="pdo-sqlite.createfunction.example.basic">
<title><methodname>Pdo\Sqlite::createFunction</methodname> example</title>
<simpara>
In this example, we have a function that calculates the SHA256 sum of a
string, and then reverses it. When the SQL statement executes, it
returns the value of the filename transformed by our function.
The data returned in <varname>$rows</varname> contains the processed result.
</simpara>
<simpara>
The beauty of this technique is that there is no need to process the
result using a &foreach; loop after the query.
</simpara>
<programlisting role="php">
<![CDATA[
<?php
function sha256_and_reverse($string)
{
return strrev(hash('sha256', $string));
}
$db = new Pdo\Sqlite('sqlite::sqlitedb');
$db->sqliteCreateFunction('sha256rev', 'sha256_and_reverse', 1);
$rows = $db->query('SELECT sha256rev(filename) FROM files')->fetchAll();
?>
]]>
</programlisting>
<!-- TODO
&example.outputs;
<screen>
<![CDATA[
Code example
]]>
</screen>
-->
</example>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<simplelist>
<member><methodname>Pdo\Sqlite::createAggregate</methodname></member>
<member><methodname>Pdo\Sqlite::createCollation</methodname></member>
<member><function>sqlite_create_function</function></member>
<member><function>sqlite_create_aggregate</function></member>
</simplelist>
</refsect1>
</refentry>
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