i just want to know if there are any alternatives to simpleXML for parsing XML Data with PHP.
For example if simpleXML module is not loaded or even if there is a lib/class out there that has a better performance then SimpleXML.
Obviously there's a ton of different way to process XML both as PHP extensions and userspace librairies. The problem is they are all much much more complicated than SimpleXML and nowhere as fast for random access.
I'm not sure what's the goal of your question though. None of those libraries/extensions share a common API so if you want a fallback in case SimpleXML isn't available then you'll have to duplicate your efforts. In actuality though, there's virtually no reason to disable SimpleXML so there's no reason to work on such a contingency plan.
You can use the DOM extension. It has the advantage many people are already familiar with DOM (coming from e.g. Javascript). Of course, DOM is very painful.
For reading large XML files, the event model (think SAX) is a necessity. See here.
Well there is XML_Parser (see http://php.net/manual/en/book.xml.php) aswell as XMLReader / XMLWriter ( http://www.php.net/manual/en/book.xmlreader.php / http://www.php.net/manual/en/book.xmlwriter.php ). SimpleXML is compiled into php per default (at least since 5.x). I can't tell you much about performance of XMLReader/XMLWriter or XML_Parser as I usually stick to SimpleXML.
Cheers,
Fabian
Related
I have two identical webpages aside from the php code. One uses SimpleXML and the other uses DOMDocument. The code edits xml files (reading, adding nodes, removing nodes).
With SimpleXML I must remove nodes using:
unset($node);
With DOMDocument, however, I use:
$node->parentNode->removeChild($node)
While the SimpleXML seems advantageous due to its brevity, it ends up taking an additional 0.4 seconds to load the page that uses SimpleXML (both pages have the same # of php lines).
What is the reason behind this performance difference? Is it the unset() function that bogs it down?
SimpleXML is an abstraction on same DOM XML library that the DOM implementation itself uses. But it is an abstraction implemented in C. That means here will be situations where SimpleXML is faster because it combines several actions on the C level and others where it is slower because it just adds syntax sugar.
If you do a lot of manipulations on an XML, using XSLT might be an even faster solution.
Like all optimization you should measure and decide.
Which is the optimal way of XML parsing(XML may be of large amount of data) in php?
See XML and PHP 5 in Devzone for a good introduction.
Basically, if you need to process large volumes of XML files, you will want to use a pull parser, like XMLReader or XMLParser to prevent running into memory issues. Parser like DOM or SimpleXML will read the whole files into memory before you can process them.
one of the most common ways is SimpleXML. it's pretty easy to use and fast.
i've used SAXY XML parser in the past. try it.
If you need a way to parse XML data that is valid for PHP4 too, then you can use the XML parser, or DOM XML (which is a PHP4 only extensions); if you need a solution for PHP5, then you can use DOM, or XMLReader.
It depends from your needs.
I have normally hand written xml like this:
<tag><?= $value ?></tag>
Having found tools such as simpleXML, should I be using those instead? What's the advantage of doing it using a tool like that?
Good XML tools will ensure that the resulting XML file properly validates against the DTD you are using.
Good XML tools also save a bunch of repetitive typing of tags.
If you're dealing with a small bit of XML, there's little harm in doing it by hand (as long as you can avoid typos). However, with larger documents you're frequently better off using an editor, which can validate your doc against the schema and protect against typos.
You could use the DOM extenstion which can be quite cumbersome to code against. My personal opinion is that the most effective way to write XML documents from ground up is the XMLWriter extension that comes with PHP and is enabled by default in recent versions.
$w=new XMLWriter();
$w->openMemory();
$w->startDocument('1.0','UTF-8');
$w->startElement("root");
$w->writeAttribute("ah", "OK");
$w->text('Wow, it works!');
$w->endElement();
echo htmlentities($w->outputMemory(true));
using a good XML generator will greatly reduce potential errors due to fat-fingering, lapse of attention, or whatever other human frailty. there are several different levels of machine assistance to choose from, however:
at the very least, use a programmer's text editor that does syntax highlighting and auto-indentation. just noticing that your text is a different color than you expect, or not lining up the way you expect, can tip you off to a typo you might otherwise have missed.
better yet, take a step back and write the XML as a data structure of whatever language you prefer, than convert that data structure to XML. Perl gives you modules such as the lightweight XML::Simple for small jobs or the heftier XML::Generator; using XML::Simple is just a matter of arranging your content into a standard Perl hash of hashes and running it through the appropriate method.
-steve
Producing XML via any sort of string manipulation opens the door for bugs to get into your code. The extremely simple example you posted, for instance, won't produce well-formed XML if $value contains an ampersand.
There aren't a lot of edge cases in XML, but there are enough that it's a waste of time to write your own code to handle them. (And if you don't handle them, your code will unexpectedly fail someday. Nobody wants that.) Any good XML tool will automatically handle those cases.
Use the generator.
The advantage of using a generator is you have consistent markup and don't run the risk of fat-fingering a bracket or quote, or forgetting to encode something. This is crucial because these mistakes will not be found until runtime, unless you have significant tests to ensure otherwise.
hand writing isn't always the best practice, because in large XML ou can write wrong tags and can be difficult to find the reason of an error. So I suggest to use XMl parsers to create XML files.
Speed may be an issue... handwritten can be a lot faster.
The XML tools in eclipse are really useful too. Just create a new xml schema and document, and you can easily use most of the graphical tools. I do like to point out that a prior understanding of how schemas work will be of use.
Always use a tool of some kind. XML can be very complex, I know that the PHP guys are used to working with hackey little stuff, but its a huge code smell in the .NET world if someone doesn't use System.XML for creating XML.
The original question is below, but I changed the title because I think it will be easier to find others with the same doubt. In the end, a XHTML document is a XML document.
It's a beginner question, but I would like to know which do you think is the best library for parsing XHTML documents in PHP5?
I have generated the XHTML from HTML files (which where created using Word :S) with Tidy, and know I need to replace some elements from them (like the and element, replace some attributes in tags).
I haven't used XML very much, there seems to be many options for parsing in PHP (Simple XML, DOM, etc.) and I don't know if all of them can do what I need, an which is the easiest one to use.
Sorry for my English, I'm form Argentina. Thanks!
I bit more information: I have a lot of HTML pages, done in Word 97. I used Tidy for cleaning and turning them in XHTML Strict, so now they are all XML compatible. I want to use an XML parser to find some elements and replace them (the logic by which I do this doesn't matter). For example, I want all of the pages to use the same CSS stylesheet and class attributes, for unified appearance. They are all static pages which contains legal documents, nothing strange there. Which of the extensions should I use? Is SimpleXML enough? Should I learn DOM in spite of being more difficult?
You could use SimpleXML, which is included in a default PHP install. This extensions offers easy object-oriented access to XML-structures.
There's also DOM XML. A "downside" to this extension is that it is a bit harder to use and that it is not included by default.
Just to clear up the confusion here. PHP has a number of XML libraries, because php4 didn't have very good options in that direction. From PHP5, you have the choice between SimpleXml, DOM and the sax-based expat parser. The latter also existed in php4. php4 also had a DOM extension, which is not the same as php5's.
DOM and SimpleXml are alternatives to the same problem domain; They læoad the document into memory and let you access it as a tree-structure. DOM is a rather bulky api, but it's also very consistent and it's implemented in many languages, meaning that you can re-use your knowledge across languages (In Javascript for example). SimpleXml may be easier initially.
The SAX parser is a different beast. It treats an xml document as a stream of tags. This is useful if you are dealing with very large documents, since you don't need to hold it all in memory.
For your usage, I would probably use the DOM api.
DOM is a standard, language-independent API for heirarchical data such as XML which has been standardized by the W3C. It is a rich API with much functionality. It is object based, in that each node is an object.
DOM is good when you not only want to read, or write, but you want to do a lot of manipulation of nodes an existing document, such as inserting nodes between others, changing the structure, etc.
SimpleXML is a PHP-specific API which is also object-based but is intended to be a lot less 'terse' than the DOM: simple tasks such as finding the value of a node or finding its child elements take a lot less code. Its API is not as rich than DOM, but it still includes features such as XPath lookups, and a basic ability to work with multiple-namespace documents. And, importantly, it still preserves all features of your document such as XML CDATA sections and comments, even though it doesn't include functions to manipulate them.
SimpleXML is very good for read-only: if all you want to do is read the XML document and convert it to another form, then it'll save you a lot of code. It's also fairly good when you want to generate a document, or do basic manipulations such as adding or changing child elements or attributes, but it can become complicated (but not impossible) to do a lot of manipulation of existing documents. It's not easy, for example, to add a child element in between two others; addChild only inserts after other elements. SimpleXML also cannot do XSLT transformations. It doesn't have things like 'getElementsByTagName' or getElementById', but if you know XPath you can still do that kind of thing with SimpleXML.
The SimpleXMLElement object is somewhat 'magical'. The properties it exposes if you var_dump/printr/var_export don't correspond to its complete internal representation. It exposes some of its child elements as if they were properties which can be accessed with the -> operator, but still preserves the full document internally, and you can do things like access a child element whose name is a reserved word with the [] operator as if it was an associative array.
You don't have to fully commit to one or the other, because PHP implements the functions:
simplexml_import_dom(DOMNode)
dom_import_simplexml(SimpleXMLElement)
This is helpful if you are using SimpleXML and need to work with code that expects a DOM node or vice versa.
PHP also offers a third XML library:
XML Parser (an implementation of SAX, a language-independent interface, but not referred to by that name in the manual) is a much lower level library, which serves quite a different purpose. It doesn't build objects for you. It basically just makes it easier to write your own XML parser, because it does the job of advancing to the next token, and finding out the type of token, such as what tag name is and whether it's an opening or closing tag, for you. Then you have to write callbacks that should be run each time a token is encountered. All tasks such as representing the document as objects/arrays in a tree, manipulating the document, etc will need to be implemented separately, because all you can do with the XML parser is write a low level parser.
The XML Parser functions are still quite helpful if you have specific memory or speed requirements. With it, it is possible to write a parser that can parse a very long XML document without holding all of its contents in memory at once. Also, if you not interested in all of the data, and don't need or want it to be put into a tree or set of PHP objects, then it can be quicker. For example, if you want to scan through an XHTML document and find all the links, and you don't care about structure.
I prefer SimpleXMLElement as it's pretty easy to use to lop through elements.
Edit: It says no version info avaliable but it's avaliable in PHP5, at least 5.2.5 but probably earlier.
It's really personal choice though, there's plenty of XML extensions.
Bear in mind many XML parsers will balk if you have invalid markup - XHTML should be XML but not always!
It's been a long time (2 years or more) since I worked with XML parsing in PHP, but I always had good, usable results from the XML_Parser Pear package. Having said that, I have had minimal exposure to PHP5, so I don't really know if there are better, inbuilt alternatives these days.
I did a little bit of XML parsing in PHP5 last year and decided to use a combination of SimpleXML.
DOM is a bit more useful if you want to create a new XML tree or add to an existing one, its slightly more flexible.
It really depends on what you're trying to accomplish.
For pulling rather large amounts of data, I.E many records of say, product information from a store website, I'd probably use Expat, since its supposedly a bit faster...
Personally, I've has XML's large enough to create a noticeable performance boost.
At those quantities you might as well be using SQL.
I recommend using SimpleXML.
It's pretty intuitive, easy to use/write.
Also, works great with XPath.
Never really got to use DOM much, but if you're using the XML Parser for something as large as you're describing you might want to use it, since its a bit more functional than SimpleXML.
You can read about all three at W3C Schools:
http://www.w3schools.com/php/php_xml_parser_expat.asp
http://www.w3schools.com/php/php_xml_simplexml.asp
http://www.w3schools.com/php/php_xml_dom.asp
I like the XMLReader class for it's simplicity and speed. But I like the xml_parse associated functions as it better allows for error recovery. It would be nice if the XMLReader class would throw exceptions for things like invalid entity refs instead of just issuinng a warning.
I'd avoid SimpleXML if you can. Though it looks very tempting by getting to avoid a lot of "ugly" code, it's just what the name suggests: simple. For example, it can't handle this:
<p>
Here is <strong>a very simple</strong> XML document.
</p>
Bite the bullet and go to the DOM Functions. The power of it far outweighs the little bit extra complexity. If you're familiar at all with DOM manipulation in Javascript, you'll feel right at home with this library.
SimpleXML seems to do a good job for me.
SimpleXML and DOM work seamlessly together, so you can use the same XML interacting with it as SimpleXML or DOM.
For example:
$simplexml = simplexml_load_string("<xml></xml>");
$simplexml->simple = "it is simple.";
$domxml = dom_import_simplexml($simplexml);
$node = $domxml->ownerDocument->createElement("dom", "yes, with DOM too.");
$domxml->ownerDocument->firstChild->appendChild($node);
echo (string)$simplexml->dom;
You will get the result:
"yes, with DOM too."
Because when you import the object (either into simplexml or dom) it uses the same underlining PHP object by reference.
I figured this out when I was trying to correct some of the errors in SimpleXML by extending/wrapping the object.
See http://code.google.com/p/blibrary/source/browse/trunk/classes/bXml.class.inc for examples.
This is really good for small chunks of XML (-2MB), as DOM/SimpleXML pull the full document into memory with some additional overhead (think x2 or x3). For large XML chunks (+2MB) you'll want to use XMLReader/XMLWriter to parse SAX style, with low memory overhead. I've used 14MB+ documents successfully with XMLReader/XMLWriter.
There are at least four options when using PHP5 to parse XML files. The best option depends on the complexity and size of the XML file.
There’s a very good 3-part article series titled ‘XML for PHP developers’ at IBM developerWorks.
“Parsing with the DOM, now fully compliant with the W3C standard, is a familiar option, and is your choice for complex but relatively small documents. SimpleXML is the way to go for basic and not-too-large XML documents, and XMLReader, easier and faster than SAX, is the stream parser of choice for large documents.”
I mostly stick to SimpleXML, at least whenever PHP5 is available for me.
http://www.php.net/simplexml