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CXLIII. SimpleXML functions
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.
The SimpleXML extension requires PHP 5.
The SimpleXML extension is enabled by default. To disable it, use the
--disable-simplexml configure option.
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 ActÓr</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;
?> |
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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..."
?> |
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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 />';
}
?> |
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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;
}
}
?> |
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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);
?> |
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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.
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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.
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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.
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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;
?> |
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shmop_write
