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CXLIV. SimpleXML functions

Introduction

The SimpleXML extension provides a very simple and easily usable toolset to convert XML to an object that can be processed with normal property selectors and array iterators.

Requirements

The SimpleXML extension requires PHP 5.

Installation

The SimpleXML extension is enabled by default. To disable it, use the --disable-simplexml configure option.

Examples

Many examples in this reference require an XML string. Instead of repeating this string in every example, we put it into a file which we include in each example. This included file is shown in the following example section. Alternatively, you could create an XML document and read it with simplexml_load_file().

Example 1. Include file example.php with XML string

<?php
$xmlstr = <<<XML
<?xml version='1.0' standalone='yes'?>
<movies>
 <movie>
  <title>PHP: Behind the Parser</title>
  <characters>
   <character>
    <name>Ms. Coder</name>
    <actor>Onlivia Actora</actor>
   </character>
   <character>
    <name>Mr. Coder</name>
    <actor>El Act&#211;r</actor>
   </character>
  </characters>
  <plot>
   So, this language. It's like, a programming language. Or is it a
   scripting language? All is revealed in this thrilling horror spoof
   of a documentary.
  </plot>
  <rating type="thumbs">7</rating>
  <rating type="stars">5</rating>
 </movie>
</movies>
XML;
?>

The simplicity of SimpleXML appears most clearly when one extracts a string or number from a basic XML document.

Example 2. Getting <plot>

<?php
include 'example.php';

$xml = new SimpleXMLElement($xmlstr);

echo $xml->movie[0]->plot; // "So this language. It's like..."
?>

Example 3. Accessing non-unique elements in SimpleXML

When multiple instances of an element exist as children of a single parent element, normal iteration techniques apply.

<?php
include 'example.php';

$xml = new SimpleXMLElement($xmlstr);

/* For each <movie> node, we echo a separate <plot>. */
foreach ($xml->movie as $movie) {
   echo $movie->plot, '<br />';
}

?>

Example 4. Using attributes

So far, we have only covered the work of reading element names and their values. SimpleXML can also access element attributes. Access attributes of an element just as you would elements of an array.

<?php
include 'example.php';

$xml = new SimpleXMLElement($xmlstr);

/* Access the <rating> nodes of the first movie.
 * Output the rating scale, too. */
foreach ($xml->movie[0]->rating as $rating) {
    switch((string) $rating['type']) { // Get attributes as element indices
    case 'thumbs':
        echo $rating, ' thumbs up';
        break;
    case 'stars':
        echo $rating, ' stars';
        break;
    }
}
?>

Example 5. Comparing Elements and Attributes with Text

To compare an element or attribute with a string or pass it into a function that requires a string, you must cast it to a string using (string). Otherwise, PHP treats the element as an object.

<?php     
include 'example.php';

$xml = new SimpleXMLElement($xmlstr);

if ((string) $xml->movie->title == 'PHP: Behind the Parser') {
    print 'My favorite movie.';
}

htmlentities((string) $xml->movie->title);
?>

Example 6. Using XPath

SimpleXML includes builtin XPath support. To find all <character> elements:

<?php
include 'example.php';
$xml = new SimpleXMLElement($xmlstr);

foreach ($xml->xpath('//character') as $character) {
    echo $character->name, 'played by ', $character->actor, '<br />';
}
?>

'//' serves as a wildcard. To specify absolute paths, omit one of the slashes.

Example 7. Setting values

Data in SimpleXML doesn't have to be constant. The object allows for manipulation of all of its elements.

<?php
include 'example.php';
$xml = new SimpleXMLElement($xmlstr);

$xml->movie[0]->characters->character[0]->name = 'Miss Coder';

echo $xml->asXML();
?>

The above code will output a new XML document, just like the original, except that the new XML will change Ms. Coder to Miss Coder.

Example 8. Adding elements and attributes

Since PHP 5.1.3, SimpleXML has had the ability to easily add children and attributes.

<?php
include 'example.php';
$xml = new SimpleXMLElement($xmlstr);

$character = $xml->movie[0]->characters->addChild('character');
$character->addChild('name', 'Mr. Parser');
$character->addChild('actor', 'John Doe');

$rating = $xml->movie[0]->addChild('rating', 'PG');
$rating->addAttribute('type', 'mpaa');

echo $xml->asXML();
?>

The above code will output an XML document based on the original but having a new character and rating.

Example 9. DOM Interoperability

PHP has a mechanism to convert XML nodes between SimpleXML and DOM formats. This example shows how one might change a DOM element to SimpleXML.

<?php
$dom = new domDocument;
$dom->loadXML('<books><book><title>blah</title></book></books>');
if (!$dom) {
     echo 'Error while parsing the document';
     exit;
}

$s = simplexml_import_dom($dom);

echo $s->book[0]->title;
?>

Table of Contents
SimpleXMLElement->addAttribute() --  Adds an attribute to the SimpleXML element
SimpleXMLElement->addChild() --  Adds a child element to the XML node
SimpleXMLElement->asXML() --  Return a well-formed XML string based on SimpleXML element
SimpleXMLElement->attributes() --  Identifies an element's attributes
SimpleXMLElement->children() --  Finds children of given node
SimpleXMLElement->__construct() --  Creates a new SimpleXMLElement object
SimpleXMLElement->getDocNamespaces() --  Returns namespaces declared in document
SimpleXMLElement->getName() -- Gets the name of the XML element
SimpleXMLElement->getNamespaces() --  Returns namespaces used in document
SimpleXMLElement->registerXPathNamespace() --  Creates a prefix/ns context for the next XPath query
SimpleXMLElement->xpath() --  Runs XPath query on XML data
simplexml_import_dom --  Get a SimpleXMLElement object from a DOM node.
simplexml_load_file --  Interprets an XML file into an object
simplexml_load_string --  Interprets a string of XML into an object
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