Original URL: https://www.theregister.com/2008/08/15/processing_xml_php/
Harness XML with PHP 5 extensions
A time to query
Posted in Software, 15th August 2008 15:02 GMT
Hands on PHP is one of the most commonly used languages for developing web sites while XML has become an industry standard for exchanging data. Increasingly, web sites use XML to transfer data through web feeds such as RSS and Atom, or through web services.
PHP 5 XML extensions provide support for parsing, transformation, XPath navigation, and schema validation of XML documents. The SimpleXML extension in PHP 5 simplifies node selection by converting an XML document to a PHP object that may be accessed with property selectors and array iterators. The XSL extension in PHP 5 is used to transform an XML document.
In this article, I'll show you how to process an example XML document, catalog.xml
using the PHP 5 XML extensions.
First things first, though. Before you go anywhere, you'll need to install PHP 5 in Apache HTTP Server, and activate the XSL extension in the php.ini
configuration file.
extension=php_xsl.dll
Restart Apache Server after modifying php.ini
.
Create your XML
To create an XML document with the PHP 5 DOM extension create a PHP file, createXML.php
, in the C:/Program Files/Apache Group/Apache2/htdocs
directory, the document root directory of the Apache server. An XML document in PHP 5 is represented with DOMDocument
class. Therefore, create a DOMDocument
object. Specify the XML version and encoding in the DOMDocument
constructor.
$domDocument = new DOMDocument('1.0','utf-8');
An element is represented with the DOMElement
class. Create root element catalog
with createElement()
. Add the root element to the DOMDocument
object with appendChild()
.
$catalog= $domDocument->createElement("catalog"); $domDocument->appendChild ($catalog);
An attribute in a DOMElement
object is represented with the DOMAttr
class. Create attribute title
with createAttribute()
. Set the value of the title
attribute using the value
property. Add the title
attribute to catalog
element using setAttributeNode()
.
$titleAttribute= $domDocument->createAttribute("title"); $titleAttribute->value="XML Zone"; $catalog->setAttributeNode ($titleAttribute);
Create a journal
element, including the date
attribute, within the catalog
element. Add an article
element, including sub elements title
and author
, within the journal
element. A text node in an element is represented with the DOMText
class. Create a text node using the createTextNode()
to set the text of title
element.
$titleText= $domDocument->createTextNode("The Java XPath API"); $title->appendChild ($titleText);
Output the XML document created to the browser using saveXML()
.
$domDocument->saveXML();
Run the PHP script with URL http://localhost/createXML.php
. The XML document, catalog.xml
, gets generated.
Parse the XML
To parse the XML document catalog.xml
create a PHP file, parseXML.php
. Create a DOMDocument
object. Load the example XML document using load(String xmlFile)
. Another function loadXML(string xmlDocument)
may be used to load an XML document from a String
.
$domDocument->load("file://C:/PHP/catalog.xml");
As an example, obtain all the title
nodes in the XML document using getElementsByTagName(string tagName)
. Iterate over the node list and output the title
elements' values.
$titleNodeList=$domDocument->getElementsByTagName("title"); for($i=0; $I<$titleNodeList->length;$i++) { echo $titleNodeList->item($i)->nodeValue; print "<br/>\n"; }
The output from the PHP script is shown below.
The Java XPath API JAXP validation
Navigate XML with XPath
To navigate the XML document using XPath create a PHP script, xpath.php
. Create a DOMDocument
object and load the example XML document with load(string filename)
.
The DOMXPath
class is used to evaluate an XPath expression in the context of an XML document node. Create a DOMXPath
object.
$domXPath=new DOMXPath($domDocument);
XPath expressions may be evaluated with query()
. Parameter of type DOMNode
is optional in query()
. By default the context node is the root element. As an example, retrieve the values of all the title
elements.
$titles=$domXPath->query("/catalog/journal/article/title");
The query()
returns a DOMNodeList
. Iterate over the DOMNodeList
to output the values of the title
elements.
foreach ($titles as $title) { echo 'Title: ', $title->firstChild->nodeValue; print "<br/>\n"; }
The output from the xpath.php
script is shown below.
Title: The Java XPath API Title: JAXP validation
Validate your XML
In this section we validate the example document with an XML schema, catalog.xsd
. The schema validation functions, schemaValidate(string filename)
and schemaValidateSource(string schema)
, return a boolean value indicating if an XML document is valid. Limitations of the schema validation functions are that only one schema may be specified for validation and that the detail of the validation error is not output.
Create a PHP script, validateXML.php
. Create a DOMDocument
object and load the XML document. Validate the XML document with the XML schema using schemaValidate()
.
$isValid=$domDocument->schemaValidate("file://C:/PHP/catalog.xsd");
The output from the PHP script is as follows.
XML Document is valid
Query XML with SimpleXML
PHP 5 provides the SimpleXML extension to select XML document nodes and node values with property selectors and array iterators. To select nodes and output node values in the XML document using the SimpleXML extension create a PHP script, simpleXML.php
. The SimpleXML extension provides functions simplexml_load_file(string filename)
and simplexml_load_string(string xmlDocument)
to load an XML document from a file or a string.
$simplexml=simplexml_load_file("file://C:/PHP/catalog.xml");
The simplexml_load_file()
converts the XML document to an object of type SimpleXMLElement
, and returns the root element in the XML document. As an example, output the value of the title
element of the article
in the first journal
element.
print $simplexml->journal->article->title;
As the $simplexml
object represents the root element in the XML document parsed, the value of the title
attribute in the root element, catalog
, is obtained as shown below.
print $simplexml['title'];
The attributes of an element may be output using attributes()
. For example, obtain the attributes in the root element.
$attributes=$simplexml->attributes();
Output the publisher
attribute.
print $attributes['publisher'];
The output is shown below.
The Java XPath API XML Zone IBM developerWorks
Transform XML
To transform the example XML document with an XSLT, catalog.xslt
, using the XSL extension, create a PHP script, transformXML.php
. Create a DOMDocument
object and load the example XML document. Create another DOMDocument
for the stylesheet and load the XSLT file.
$xslFile=new DOMDocument(); $xslFile->load("file://C:/PHP/catalog.xslt");
An XML document is transformed using an XSLTProcessor
. Therefore, create an XSLTProcessor
.
$xsltProcessor=new XSLTProcessor();
An XSLT stylesheet is imported into the XSLT processor for transformations with importStylesheet(DOMDocument)
.
$xsltProcessor->importStylesheet($xslFile);
Transform the XML document with the XSLT file using transformToXML()
, and output the result of the transformation.
echo $xsltProcessor->transformToXML($domDocument);
The output from the XSLT transformation gets displayed in the browser.
There you have it: you have just parsed, navigated, transformed and validated an XML document using the PHP 5 XML extensions. As noted, my PHP 5 scripts were run in Apache but you can use any web server that supports PHP.®