SimpleXML insert Processing Instruction (Stylesheet) - php

Question

I want to integrate an XSL file in an XML string gived me by php CURL command.
I tryed this
$output = XML gived me by curl option;
$hotel = simplexml_load_string($output);
$hotel->addAttribute('?xml-stylesheet type=”text/xsl” href=”css/stile.xsl”?');
echo $hotel->asXML();
Doing this when I see the XML on browser, I receive the file without the stylesheet.
Where is my error?

Answer 1

A SimpleXMLElement does not allow you by default to create and add a Processing Instruction (PI) to a node. However the sister library DOMDocument allows this. You can marry the two by extending from SimpleXMLElement and create a function to provide that feature:
class MySimpleXMLElement extends SimpleXMLElement
{
public function addProcessingInstruction($target, $data = NULL) {
$node = dom_import_simplexml($this);
$pi = $node->ownerDocument->createProcessingInstruction($target, $data);
$result = $node->appendChild($pi);
return $this;
}
}
This then is easy to use:
$output = '<hotel/>';
$hotel = simplexml_load_string($output, 'MySimpleXMLElement');
$hotel->addProcessingInstruction('xml-stylesheet', 'type="text/xsl" href="style.xsl"');
$hotel->asXML('php://output');
Exemplary output (beautified):
<?xml version="1.0"?>
<hotel>
<?xml-stylesheet type="text/xsl" href="style.xsl"?>
</hotel>
Another way is to insert an XML chunk to a simplexml element: "PHP SimpleXML: insert node at certain position" or "Insert XML into a SimpleXMLElement".