XML operation of PHP extension (1)-SimpleXML

1. Introduction and installation

SimpleXML extension provides a very simple and easy-to-use toolset that can convert XML into an XML file with general attribute selectors and An object for array iterators.

This extension requires the libxml PHP extension. This means that --enable-libxml needs to be used, although this will be done implicitly since libxml is enabled by default.

Requires PHP5 and above.

This extension is enabled by default and can be disabled through the following options when compiling: --disable-simplexml

2. Usage examples

Basic usage

Example #1 Include file example.php with XML string

<?php
$xmlstr = <<<XML
<?xml version=&#39;1.0&#39; standalone=&#39;yes&#39;?>
<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&#39;s like, a programming language. Or is it a
scripting language? All is revealed in this thrilling horror spoof
of a documentary.
</plot>
<great-lines>
<line>PHP solves all my web problems</line>
</great-lines>
<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 a82a54010e8e844b28dec6f52c796df1

<?phpinclude &#39;example.php&#39;;
$movies = new SimpleXMLElement($xmlstr);
echo $movies->movie[0]->plot;?>

The above routine will output:

   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.

Accessing elements within an XML document that contain characters not permitted under PHP's naming convention (e.g. the hyphen) can be accomplished by encapsulating the element name within braces and the apostrophe.

Example #3 Getting 15a73cc5312745b1b00671f6e690e36a

<?phpinclude &#39;example.php&#39;;
$movies = new SimpleXMLElement($xmlstr);
echo $movies->movie->{&#39;great-lines&#39;}->line;?>

The above routine will output:

PHP solves all my web problems

Example #4 Accessing non-unique elements in SimpleXML

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

<?phpinclude &#39;example.php&#39;;
$movies = new SimpleXMLElement($xmlstr);
/* For each <character> node, we echo a separate <name>. */foreach ($movies->movie->characters->character as $character) {
echo $character->name, &#39; played by &#39;, $character->actor, PHP_EOL;}
?>

The above routine will output:

Ms. Coder played by Onlivia Actora
Mr. Coder played by El ActÓr

Note:

Properties ($movies->movie in previous example) are not arrays. They are iterable and accessible objects.

Example #5 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.

<?phpinclude &#39;example.php&#39;;
$movies = new SimpleXMLElement($xmlstr);
/* Access the <rating> nodes of the first movie.* Output the rating scale, too. */
foreach ($movies->movie[0]->rating as $rating) {
switch((string) $rating[&#39;type&#39;]) { // Get attributes as element indicescase &#39;thumbs&#39;:echo $rating, &#39; thumbs up&#39;;
break;case &#39;stars&#39;:echo $rating, &#39; stars&#39;;break;}}
?>

The above routine will output:

7 thumbs up5 stars

Example #6 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.

<?phpinclude &#39;example.php&#39;;
$movies = new SimpleXMLElement($xmlstr);
if ((string) $movies->movie->title == &#39;PHP: Behind the Parser&#39;) {print &#39;My favorite movie.&#39;;}
echo htmlentities((string) $movies->movie->title);?>

The above routine will output:

My favorite movie.PHP: Behind the Parser

Example #7 Comparing Two Elements

Two SimpleXMLElements are considered different even if they point to the same element since PHP 5.2.0.

<?phpinclude &#39;example.php&#39;;
$movies1 = new SimpleXMLElement($xmlstr);$movies2 = new SimpleXMLElement($xmlstr);
var_dump($movies1 == $movies2); // false since PHP 5.2.0?>

The above routine will output:

bool(false)

Example #8 Using XPath

SimpleXML includes built-in support. To find all db0c08544b71179f3fd0e855bd613a1b elements:

<?phpinclude &#39;example.php&#39;;
$movies = new SimpleXMLElement($xmlstr);
foreach ($movies->xpath(&#39;//character&#39;) as $character) {
echo $character->name, &#39;played by &#39;, $character->actor, PHP_EOL;}?>

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

The above routine will output:

Ms. Coder played by Onlivia Actora
Mr. Coder played by El ActÓr

Example #9 Setting values

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

<?phpinclude &#39;example.php&#39;;$movies = new SimpleXMLElement($xmlstr);
$movies->movie[0]->characters->character[0]->name = &#39;Miss Coder&#39;;
echo $movies->asXML();?>

The above routine will output:

3e5184b51d19bd3b3173071244ff71fe
eab6e99f51fee68293d1126fa516c747
 8adf8e6c41d19c74d254355bd9d9c69e
  b2386ffb911b14667cb8f0f91ea547a7PHP: Behind the Parser6e916e0f7d1e588d4f442bf645aedb2f
  c3ae6056e653b437c6b27357b7e7671a
   db0c08544b71179f3fd0e855bd613a1b
    8a11bc632ea32a57b3e3693c7987c420Miss Coderdf406f776eecbaf16b62325323196f14
    194eaccae6455d5c407b1ac2afe04cd0Onlivia Actorac0d1bcc4fa4e9e034ebc23e1ef89e5c2
   66707054a46c2dec1bf24d9318ba1124
   db0c08544b71179f3fd0e855bd613a1b
    8a11bc632ea32a57b3e3693c7987c420Mr. Coderdf406f776eecbaf16b62325323196f14
    194eaccae6455d5c407b1ac2afe04cd0El ActÓrc0d1bcc4fa4e9e034ebc23e1ef89e5c2
   66707054a46c2dec1bf24d9318ba1124
  aabc3226380a602ad187eb87d5efa83f
  a82a54010e8e844b28dec6f52c796df1
   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.
  fa8825681e04013deb51ef36ab6dbac6
  54a9d3919a9de3703b391ab1e4eaee87
   15a73cc5312745b1b00671f6e690e36aPHP solves all my web problems6e6d7ec7f2f63fbe473136c2c34a55b7
  c0dd7eda886ba0d09f5a00454545474c
  e27af9d8c16e5d4022ce762c86f195be79df14055a92f49c29299ca2d367bde62
  b724a65f9508b61211142b27c8620c4659df14055a92f49c29299ca2d367bde62
 96664a6d22a82ab9c28a528afca408bc
c3a75a871bc1ee80ecb54700c0759808

Example #10 Adding elements and attributes

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

<?phpinclude &#39;example.php&#39;;$movies = new SimpleXMLElement($xmlstr);
$character = $movies->movie[0]->characters->addChild(&#39;character&#39;);$character->addChild(&#39;name&#39;, &#39;Mr. Parser&#39;);
$character->addChild(&#39;actor&#39;, &#39;John Doe&#39;);
$rating = $movies->movie[0]->addChild(&#39;rating&#39;, &#39;PG&#39;);$rating->addAttribute(&#39;type&#39;, &#39;mpaa&#39;);
echo $movies->asXML();?>

The above routine will output ：

3e5184b51d19bd3b3173071244ff71fe
eab6e99f51fee68293d1126fa516c747
 8adf8e6c41d19c74d254355bd9d9c69e
  b2386ffb911b14667cb8f0f91ea547a7PHP: Behind the Parser6e916e0f7d1e588d4f442bf645aedb2f
  c3ae6056e653b437c6b27357b7e7671a
   db0c08544b71179f3fd0e855bd613a1b
    8a11bc632ea32a57b3e3693c7987c420Ms. Coderdf406f776eecbaf16b62325323196f14
    194eaccae6455d5c407b1ac2afe04cd0Onlivia Actorac0d1bcc4fa4e9e034ebc23e1ef89e5c2
   66707054a46c2dec1bf24d9318ba1124
   db0c08544b71179f3fd0e855bd613a1b
    8a11bc632ea32a57b3e3693c7987c420Mr. Coderdf406f776eecbaf16b62325323196f14
    194eaccae6455d5c407b1ac2afe04cd0El ActÓrc0d1bcc4fa4e9e034ebc23e1ef89e5c2
   66707054a46c2dec1bf24d9318ba1124
  db0c08544b71179f3fd0e855bd613a1b8a11bc632ea32a57b3e3693c7987c420Mr. Parserdf406f776eecbaf16b62325323196f14194eaccae6455d5c407b1ac2afe04cd0John Doec0d1bcc4fa4e9e034ebc23e1ef89e5c266707054a46c2dec1bf24d9318ba1124aabc3226380a602ad187eb87d5efa83f
  a82a54010e8e844b28dec6f52c796df1
   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.
  fa8825681e04013deb51ef36ab6dbac6
  54a9d3919a9de3703b391ab1e4eaee87
   15a73cc5312745b1b00671f6e690e36aPHP solves all my web problems6e6d7ec7f2f63fbe473136c2c34a55b7
  c0dd7eda886ba0d09f5a00454545474c
  e27af9d8c16e5d4022ce762c86f195be79df14055a92f49c29299ca2d367bde62
  b724a65f9508b61211142b27c8620c4659df14055a92f49c29299ca2d367bde62
 8f35ab349d6453d281f32443bf3504f4PG9df14055a92f49c29299ca2d367bde6296664a6d22a82ab9c28a528afca408bc
c3a75a871bc1ee80ecb54700c0759808

Example #11 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(&#39;<books><book>
<title>blah</title></book></books>&#39;);if (!$dom) {echo &#39;Error while parsing the document&#39;;exit;}
$books = simplexml_import_dom($dom);
echo $books->book[0]->title;?>

The above routine will output:

blah

Handling XML errors

Example #1 Loading broken XML string

<?php
libxml_use_internal_errors(true);
$sxe = simplexml_load_string("<?xml version=&#39;1.0&#39;><broken><xml></broken>");
if ($sxe === false) {
echo "Failed loading XML\n";
foreach(libxml_get_errors() as $error) {
echo "\t", $error->message;
}
}
?>

The above routine will output:

Failed loading XML
    Blank needed here
    parsing XML declaration: '?>' expected
    Opening and ending tag mismatch: xml line 1 and broken
    Premature end of data in tag broken line 1

3. Related functions

• 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

4. Related classes and member functions

SimpleXMLElement class

• ##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::count — Counts the children of an element

• 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::saveXML — 别名 SimpleXMLElement::asXML

• SimpleXMLElement::__toString — Returns the string content

• SimpleXMLElement::xpath — Runs XPath query on XML data

SimpleXMLIterator类

• SimpleXMLIterator::current — Returns the current element

• SimpleXMLIterator::getChildren — Returns the sub-elements of the current element

• SimpleXMLIterator::hasChildren — Checks whether the current element has sub elements.

• SimpleXMLIterator::key — Return current key

• SimpleXMLIterator::next — Move to next element

• SimpleXMLIterator::rewind — Rewind to the first element

• SimpleXMLIterator::valid — Check whether the current element is valid

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