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-- Provided by anonymous 64041 (jan.slabon@setasign.com) git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@338389 c90b9560-bf6c-de11-be94-00142212c4b1
135 lines
4.2 KiB
XML
135 lines
4.2 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<chapter xml:id="pdo.lobs" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
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<title>Large Objects (LOBs)</title>
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<para>
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At some point in your application, you might find that you need to store
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"large" data in your database. Large typically means "around 4kb or
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more", although some databases can happily handle up to 32kb before data becomes
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"large". Large objects can be either textual or binary in nature. PDO
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allows you to work with this large data type by using the
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<constant>PDO::PARAM_LOB</constant>
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type code in your <function>PDOStatement::bindParam</function> or
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<function>PDOStatement::bindColumn</function> calls.
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<constant>PDO::PARAM_LOB</constant> tells
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PDO to map the data as a stream, so that you can manipulate it using the
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<link linkend="ref.stream">PHP Streams API</link>.
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</para>
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<para>
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<example>
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<title>Displaying an image from a database</title>
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<para>
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This example binds the LOB into the variable named $lob and then sends
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it to the browser using <function>fpassthru</function>. Since the LOB
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is represented as a stream, functions such as
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<function>fgets</function>, <function>fread</function> and
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<function>stream_get_contents</function> can be used on it.
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</para>
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<programlisting role="php">
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<![CDATA[
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<?php
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$db = new PDO('odbc:SAMPLE', 'db2inst1', 'ibmdb2');
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$stmt = $db->prepare("select contenttype, imagedata from images where id=?");
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$stmt->execute(array($_GET['id']));
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$stmt->bindColumn(1, $type, PDO::PARAM_STR, 256);
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$stmt->bindColumn(2, $lob, PDO::PARAM_LOB);
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$stmt->fetch(PDO::FETCH_BOUND);
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header("Content-Type: $type");
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fpassthru($lob);
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?>
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]]>
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</programlisting>
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</example>
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</para>
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<para>
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<example>
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<title>Inserting an image into a database</title>
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<para>
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This example opens up a file and passes the file handle to PDO to insert
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it as a LOB. PDO will do its best to get the contents of the file up
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to the database in the most efficient manner possible.
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</para>
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<programlisting role="php">
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<![CDATA[
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<?php
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$db = new PDO('odbc:SAMPLE', 'db2inst1', 'ibmdb2');
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$stmt = $db->prepare("insert into images (id, contenttype, imagedata) values (?, ?, ?)");
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$id = get_new_id(); // some function to allocate a new ID
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// assume that we are running as part of a file upload form
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// You can find more information in the PHP documentation
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$fp = fopen($_FILES['file']['tmp_name'], 'rb');
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$stmt->bindParam(1, $id);
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$stmt->bindParam(2, $_FILES['file']['type']);
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$stmt->bindParam(3, $fp, PDO::PARAM_LOB);
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$db->beginTransaction();
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$stmt->execute();
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$db->commit();
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?>
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]]>
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</programlisting>
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</example>
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</para>
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<para>
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<example>
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<title>Inserting an image into a database: Oracle</title>
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<para>
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Oracle requires a slightly different syntax for inserting a lob from a
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file. It's also essential that you perform the insert under a
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transaction, otherwise your newly inserted LOB will be committed with a
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zero-length as part of the implicit commit that happens when the query
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is executed:
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</para>
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<programlisting role="php">
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<![CDATA[
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<?php
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$db = new PDO('oci:', 'scott', 'tiger');
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$stmt = $db->prepare("insert into images (id, contenttype, imagedata) " .
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"VALUES (?, ?, EMPTY_BLOB()) RETURNING imagedata INTO ?");
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$id = get_new_id(); // some function to allocate a new ID
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// assume that we are running as part of a file upload form
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// You can find more information in the PHP documentation
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$fp = fopen($_FILES['file']['tmp_name'], 'rb');
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$stmt->bindParam(1, $id);
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$stmt->bindParam(2, $_FILES['file']['type']);
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$stmt->bindParam(3, $fp, PDO::PARAM_LOB);
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$db->beginTransaction();
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$stmt->execute();
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$db->commit();
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?>
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]]>
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</programlisting>
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</example>
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</para>
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</chapter>
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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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