使用XMLWriter将变量数据输出为CDATA XML

Question

I'm trying to make a web service in PHP for an app to communicate with that will get data from a database and put it into XML format for the app. One of the columns, however, contains HTML and needs to be outputted (I think) as CDATA. I'm having trouble accomplishing this though. Please advise

<?php
mysql_connect(DB_HOST, DB_USER, DB_PASSWORD);
mysql_select_db(DB_NAME);

$sql = "SELECT post_date_gmt, post_content, post_title FROM [schema].wp_posts WHERE post_status = \"publish\" && post_type = \"post\" ORDER BY post_date_gmt DESC;";
$res = mysql_query($sql);

$xml = new XMLWriter();

$xml->openURI("php://output");
$xml->startDocument();
$xml->setIndent(true);

$xml->startElement('BlogPosts');

while ($row = mysql_fetch_assoc($res)) {

    $xml->startElement("Post");

    $xml->startElement("PostDate");
    $xml->writeRaw($row['post_date_gmt']);
    $xml->endElement();

    $xml->startElement("PostTitle");
    $xml->$writeRaw($row['post_title']);
    $xml->endElement();

    $xml->startCData("PostContent");
    $xml->writeCData($row['post_content']);
    $xml->endCData();

    $xml->endElement();

}

$xml->endElement();

header('Content-type: text/xml');
$xml->flush();

?>

Thank you very much in advance for any assistance you could offer!

Answer 1

Do not use XMLWriter::writeRaw(), except if you really want to write XML fragments directly. "Raw" means that here will be no escaping from the library.

The correct way to write text into the XML document is XMLWriter::text().

$xml->startElement('PostTitle');
$xml->text('foo & bar');
$xml->endElement();

Output:

<?xml version="1.0"?>
<PostTitle>foo &amp; bar</PostTitle>

If you use XMLWriter::writeRaw() in this example the result would contain an unescaped & and be invalid XML.

CDATA sections are character nodes not unlike text nodes, but allow special characters without escaping and keep whitespaces. You always have to create the element node separately. An element node can contain multiple other nodes, even multiple CDATA sections.

XmlReader has two ways to create CDATA sections:

A single method:

$xml->startElement("PostContent");
$xml->writeCData('<b>post</b> content');
$xml->endElement();

Output:

<?xml version="1.0"?>
<PostContent><![CDATA[<b>post</b> content]]></PostContent>

Or start/end methods:

$xml->startElement("PostContent");
$xml->startCData();
$xml->text('<b>post</b> content');
$xml->text(' more content');
$xml->endCData();
$xml->endElement();

Output:

<?xml version="1.0"?>
<PostContent><![CDATA[<b>post</b> content more content]]></PostContent>