archived-doc-en/reference/pdo_sqlite/pdo/sqlite/createfunction.xml

<?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->createFunction('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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