带样式表的CakePHP XmlView（XSL）

Question

I'm using cakephp's Xml or XmlView with _serialize to translate an array to xml, however I cannot add a stylesheet declaration.

Is it possible to add: into the XML before the root tag when using Array to XML?

Sample code:

$value = array(
    'tags' => array(
        'tag' => array(
            array(
                'id' => '1',
                'name' => 'defect'
            ),
            array(
                'id' => '2',
                'name' => 'enhancement'
        )
        )
    )
);
$xml = Xml::build($value);
echo $xml->asXML();

Answer 1

Use built-in DOMDocument methods

Xml::build() returns an instance of either SimpleXMLElement (default) or DOMDocument. The latter has a built-in method for creating processing instruction nodes, DOMDocument::createProcessingInstruction().

$xml = Xml::build($value, array('return' => 'domdocument'));
$style = $xml->createProcessingInstruction(
    'xml-stylesheet',
    'type="text/xsl" href="/path/to/style.xsl"'
);
$xml->insertBefore($style, $xml->firstChild);
echo $xml->saveXML();

This would output something like:

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="/path/to/style.xsl"?>
<tags>
    ...
</tags>

See also

• http://book.cakephp.org/2.0/en/core-utility-libraries/xml.html#Xml::build
• http://www.php.net/manual/en/domdocument.createprocessinginstruction.php

Manipulating XmlView output

When using XmlView there is no way to hook into the XML generation process, as it's finally generated using a simple one-liner:

return Xml::fromArray($data, $options)->asXML();

So the only option here would be to take the generated output and process it again. For example extend the XmlView, override the _serialize() method, and then take that generated output, create a new DOMDocument instance from it, and add the PI nodes if necessary.

Here's an (untested) example of such an exteneded view:

App::uses('XmlView', 'View');

class MyXmlView extends XmlView {
    protected function _serialize($serialize) {
        $xml = parent::_serialize($serialize);

        if(isset($this->viewVars['_processingInstructions'])) {
            $pi = array_reverse($this->viewVars['_processingInstructions']);

            $doc = new DOMDocument();
            $doc->loadXML($xml);

            foreach($pi as $instruction) {
                $node = $doc->createProcessingInstruction(
                    current(array_keys($instruction)),
                    current($instruction)
                );
                $doc->insertBefore($node, $doc->firstChild);
            }

            $xml = $doc->saveXML();
        }

        return $xml;
    }
}

In the controller one could then set the _processingInstructions view variable to define PI nodes:

$_processingInstructions = array(
    array('xml-stylesheet' => 'type="text/xsl" href="/path/to/style.xsl"')
);

$this->set(compact('tags', '_processingInstructions'));
$this->set('_serialize', 'tags');