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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 317502 $ -->
<chapter xml:id="pdo.lobs" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<title>Large Objects (LOBs)</title>
<para>
At some point in your application, you might find that you need to store
"large" data in your database. Large typically means "around 4kb or
more", although some databases can happily handle up to 32kb before data becomes
"large". Large objects can be either textual or binary in nature. PDO
allows you to work with this large data type by using the
<constant>PDO::PARAM_LOB</constant>
type code in your <function>PDOStatement::bindParam</function> or
<function>PDOStatement::bindColumn</function> calls.
<constant>PDO::PARAM_LOB</constant> tells
PDO to map the data as a stream, so that you can manipulate it using the
<link linkend="ref.stream">PHP Streams API</link>.
</para>
<para>
<example>
<title>Displaying an image from a database</title>
<para>
This example binds the LOB into the variable named $lob and then sends
it to the browser using <function>fpassthru</function>. Since the LOB
is represented as a stream, functions such as
<function>fgets</function>, <function>fread</function> and
<function>stream_get_contents</function> can be used on it.
</para>
<programlisting role="php">
<![CDATA[
<?php
$db = new PDO('odbc:SAMPLE', 'db2inst1', 'ibmdb2');
$stmt = $db->prepare("select contenttype, imagedata from images where id=?");
$stmt->execute(array($_GET['id']));
$stmt->bindColumn(1, $type, PDO::PARAM_STR, 256);
$stmt->bindColumn(2, $lob, PDO::PARAM_LOB);
$stmt->fetch(PDO::FETCH_BOUND);
header("Content-Type: $type");
fpassthru($lob);
?>
]]>
</programlisting>
</example>
</para>
<para>
<example>
<title>Inserting an image into a database</title>
<para>
This example opens up a file and passes the file handle to PDO to insert
it as a LOB. PDO will do its best to get the contents of the file up
to the database in the most efficient manner possible.
</para>
<programlisting role="php">
<![CDATA[
<?php
$db = new PDO('odbc:SAMPLE', 'db2inst1', 'ibmdb2');
$stmt = $db->prepare("insert into images (id, contenttype, imagedata) values (?, ?, ?)");
$id = get_new_id(); // some function to allocate a new ID
// assume that we are running as part of a file upload form
// You can find more information in the PHP documentation
$fp = fopen($_FILES['file']['tmp_name'], 'rb');
$stmt->bindParam(1, $id);
$stmt->bindParam(2, $_FILES['file']['type']);
$stmt->bindParam(3, $fp, PDO::PARAM_LOB);
$db->beginTransaction();
$stmt->execute();
$db->commit();
?>
]]>
</programlisting>
</example>
</para>
<para>
<example>
<title>Inserting an image into a database: Oracle</title>
<para>
Oracle requires a slightly different syntax for inserting a lob from a
file. It's also essential that you perform the insert under a
transaction, otherwise your newly inserted LOB will be committed with a
zero-length as part of the implicit commit that happens when the query
is executed:
</para>
<programlisting role="php">
<![CDATA[
<?php
$db = new PDO('oci:', 'scott', 'tiger');
$stmt = $db->prepare("insert into images (id, contenttype, imagedata) " .
"VALUES (?, ?, EMPTY_BLOB()) RETURNING imagedata INTO ?");
$id = get_new_id(); // some function to allocate a new ID
// assume that we are running as part of a file upload form
// You can find more information in the PHP documentation
$fp = fopen($_FILES['file']['tmp_name'], 'rb');
$stmt->bindParam(1, $id);
$stmt->bindParam(2, $_FILES['file']['type']);
$stmt->bindParam(3, $fp, PDO::PARAM_LOB);
$stmt->beginTransaction();
$stmt->execute();
$stmt->commit();
?>
]]>
</programlisting>
</example>
</para>
</chapter>
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