php-lyte-xml

The base classes for XML work in php have a few little quirks that annoy me a lot, this is a simple collection of fixes for those annoyances.

Some of what I'm trying to put in is going to be purely experimental, so use at you're own risk :)

Examples

Nested CDATA in XMLWriter
XMLReader expanded DOMNodes actually have ownerDocuments
Lazy XPaths - XPaths that actually work in a OO manner
Contextified DOMNode XPath functions
Key/Value pair iterator
saveXML() anywhere
Translate to UTF8 on the fly

Nested CDATA in XMLWriter

There's a fairly well known method for working around the fact that XML doesn't actually let you nest a CDATA tag inside another one, but XMLWriter doesn't bother to apply this fix for you. Which is a problem if for instance you're transporting HTML fragments within another XML format.

With XMLWriter:

$writer = new XMLWriter();
$writer->openMemory();
$writer->writeCData('<![CDATA[a little bit of cdata]]>');
echo $writer->flush()."\n";

will result in:

<![CDATA[<![CDATA[a little bit of cdata]]>]]>

which isn't valid XML!

Use LyteXMLWriter instead and you'll get something that works the way you expect:

$writer = new LyteXMLWriter();
$writer->openMemory();
$writer->writeCData('<![CDATA[a little bit of cdata]]>');
echo $writer->flush()."\n";

will result in:

<![CDATA[<![CDATA[a little bit of cdata]]]]><![CDATA[>]]>

Expanding to a DOMNode from XMLReader

With the default XMLReader if you call expand() you get back a DOMNode, which is nice, but it has its ownerDocument property set to null, which makes things like using a DOMXPath or saving it to an XML string snippet quite difficult.

E.g. with the normal XMLReader:

$reader = new XMLReader();
$reader->xml('<foo>bar</foo>');
$reader->read();
$node = $reader->expand();
echo $node->ownerDocument->saveXML();

results in:

PHP Fatal error:  Call to a member function saveXML() on a non-object in - on line 6

... oops!

With LyteXMLReader if you expand a node it creates the ownerDocument for you though:

$reader = new LyteXMLReader();
$reader->xml('<foo>bar</foo>');
$reader->read();
$node = $reader->expand();
echo $node->ownerDocument->saveXML();

works this time:

<?xml version="1.0"?>
<foo>bar</foo>

Lazy XPaths

PHP has fairly relaible XPath support in the form of DOMXPath, but it's not directly attached to anything, breaking your nice OO context because now you either need to pass around two objects or continually reinstatiate your DOMXPath object.

LyteDOMDocument will lazily create a DOMXPath object for use if you just ask for it, e.g. with regular DOMDocument:

$doc = new DOMDocument();
$doc->load('<foo/>');
$xpath = new DOMXPath($doc);
// and now I've got to pass around $doc and $xpath or recreate $xpath many times

with LyteDOMDocument:

$doc = new LyteDOMDocument();
$doc->loadXML('<foo/>');
// now I can just use the xpath (the xpath property gets instantiated to a LyteDOMXPath as it's requested)
$nodes = $doc->xpath->query('/foo');

Contextified DOMNode XPath functions

Normally to run a XPath under a specific context you have to do a fair bit of set up, e.g.:

$doc = new DOMDocument();
$doc->loadXML('<root><foo>one</foo><foo>two</foo></root>');
$xpath = new DOMXPath($doc);
$node = $doc->firstChild;
$nodes = $xpath->query('foo/text()', $node);

but LyteDOMNode provides XPath functions directly that are already contextified:

$doc = new LyteDOMDocument();
$doc->loadXML('<root><foo>one</foo><foo>two</foo></root>');
$nodes = $doc->firstChild->xPathQuery('foo/text()');

There's also a LyteDOMNode::xPathEvaluate() function that's synonymous with DOMXPath::evaluate() with the context already filled out.

Key/Value pair iterator

I seem to have to parse XML with key pairs a lot, e.g:

<root>
	<key1>value1</key1>
	<key2>value2</key2>
	...
	<key3>value3</key3>
</root>

With LyteDOMNodeList I've provided a toPairs() function to simplify this operation:

// once you have a node with the key/pairs in it:
$node = ...;
// you can just iterate over it:
foreach ($node->childNodes->toPairs() as $k => $v) {
	...
}

saveXML() anywhere

There's a commonish trick to get the XML just of a subtree of an XML DOM using ownerDocument like so:

$xml = $node->ownerDocument->saveXML($node);

with a LyteDOMNode you can just ask it to save the XML directly:

$xml = $node->saveXML();

Translate to UTF8 on the fly

LyteXMLWriter

Simply state what the source encoding is and have it transcoded on the fly, e.g:

$writer = new LyteXMLWriter();
$writer->openMemory();
$writer->setSourceCharacterEncoding('Windows-1252');
$writer->text("Don\x92t you hate word quotes?\n");
echo $writer->flush();

Produces:

Don’t you hate word quotes?

LyteDOMDocument::loadHTML()

Load HTML from an arbitrary character set:

$dom = new LyteDOMDocument();
$html = "<p>\x93bendy quotes\x94</p>";
$encoding = 'Windows-1252';
$dom->loadHTML($html, $encoding);

Caveats

Most of the classes I've created do not directly inherit from the XML ones, e.g. new LyteDOMDocument() instanceof DOMDocument is false. I've currently done this because to avoid duplicating memory all over the place and reserializing too much of the XML, I really need to use the decorator pattern, but even with PHP's magic methods I can't find a way to both inherit and decorate an object. I've even looked in to using the Reflection API to walk the upstream classes and selectively eval a new class in to existence, but ran in to problems with many of public properties getting updated at odd times by the base DOM classes.

The net result is a bunch of objects that walk like ducks, talk like ducks, but you might have trouble in weird corner cases convincing PHP that they're ducks, but still send me any bugs when you run in to issues.

If anyone can solve this, lodge an issue :)

benagricola / php-lyte-xml