Basic SimpleXML usage

目录搜索

文字

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>
  <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 <plot>

  <?php
 include  'example.php' ;

 $movies  = new  SimpleXMLElement ( $xmlstr );

echo  $movies -> movie [ 0 ]-> plot ;
 ?>

以上例程会输出：

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 <line>

  <?php
 include  'example.php' ;

 $movies  = new  SimpleXMLElement ( $xmlstr );

echo  $movies -> movie ->{ 'great-lines' }-> line ;
 ?>

以上例程会输出：

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.

  <?php
 include  'example.php' ;

 $movies  = new  SimpleXMLElement ( $xmlstr );

 
 foreach ( $movies -> movie -> characters -> character  as  $character ) {
   echo  $character -> name ,  ' played by ' ,  $character -> actor ,  PHP_EOL ;
}

 ?>

以上例程会输出：

Ms. Coder played by Onlivia Actora
Mr. Coder played by El Act?r

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 .

  <?php
 include  'example.php' ;

 $movies  = new  SimpleXMLElement ( $xmlstr );

 
 foreach ( $movies -> 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;
    }
}
 ?>

以上例程会输出：

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.

  <?php
 include  'example.php' ;

 $movies  = new  SimpleXMLElement ( $xmlstr );

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

echo  htmlentities ((string)  $movies -> movie -> title );
 ?>

以上例程会输出：

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.

  <?php
 include  'example.php' ;

 $movies1  = new  SimpleXMLElement ( $xmlstr );
 $movies2  = new  SimpleXMLElement ( $xmlstr );
 var_dump ( $movies1  ==  $movies2 );  // false since PHP 5.2.0
 ?>

以上例程会输出：

bool(false)

Example #8 Using XPath

SimpleXML includes built-in XPath support. To find all <character> elements:

  <?php
 include  'example.php' ;

 $movies  = new  SimpleXMLElement ( $xmlstr );

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

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

以上例程会输出：

Ms. Coder played by Onlivia Actora
Mr. Coder played by El Act?r

Example #9 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' ;
 $movies  = new  SimpleXMLElement ( $xmlstr );

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

echo  $movies -> asXML ();
 ?>

以上例程会输出：

<?xml version="1.0" standalone="yes"?>
<movies>
 <movie>
  <title>PHP: Behind the Parser</title>
  <characters>
   <character>
    <name>Miss Coder</name>
    <actor>Onlivia Actora</actor>
   </character>
   <character>
    <name>Mr. Coder</name>
    <actor>El Act&#xD3;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>
  <great-lines>
   <line>PHP solves all my web problems</line>
  </great-lines>
  <rating type="thumbs">7</rating>
  <rating type="stars">5</rating>
 </movie>
</movies>

Example #10 Adding elements and attributes

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

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

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

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

echo  $movies -> asXML ();
 ?>

以上例程会输出：

<?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&#xD3;r</actor>
   </character>
  <character><name>Mr. Parser</name><actor>John Doe</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>
  <great-lines>
   <line>PHP solves all my web problems</line>
  </great-lines>
  <rating type="thumbs">7</rating>
  <rating type="stars">5</rating>
 <rating type="mpaa">PG</rating></movie>
</movies>

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 ( '<books><book><title>blah</title></book></books>' );
if (! $dom ) {
    echo  'Error while parsing the document' ;
    exit;
}

 $books  =  simplexml_import_dom ( $dom );

echo  $books -> book [ 0 ]-> title ;
 ?>

以上例程会输出：

blah

用户评论:

[#1] rowan dot collins at gmail dot com [2015-06-04 18:58:57]

There is a common "trick" often proposed to convert a SimpleXML object to an array, by running it through json_encode() and then json_decode(). I'd like to explain why this is a bad idea.

Most simply, because the whole point of SimpleXML is to be easier to use and more powerful than a plain array. For instance, you can write <?php $foo->bar->baz['bing'] ?> and it means the same thing as <?php $foo->bar[0]->baz[0]['bing'] ?>, regardless of how many bar or baz elements there are in the XML; and if you write <?php (string)$foo->bar[0]->baz[0] ?> you get all the string content of that node - including CDATA sections - regardless of whether it also has child elements or attributes. You also have access to namespace information, the ability to make simple edits to the XML, and even the ability to "import" into a DOM object, for much more powerful manipulation. All of this is lost by turning the object into an array rather than reading understanding the examples on this page.

Additionally, because it is not designed for this purpose, the conversion to JSON and back will actually lose information in some situations. For instance, any elements or attributes in a namespace will simply be discarded, and any text content will be discarded if an element also has children or attributes. Sometimes, this won't matter, but if you get in the habit of converting everything to arrays, it's going to sting you eventually.

Of course, you could write a smarter conversion, which didn't have these limitations, but at that point, you are getting no value out of SimpleXML at all, and should just use the lower level XML Parser functions, or the XMLReader class, to create your structure. You still won't have the extra convenience functionality of SimpleXML, but that's your loss.

[#2] mymymymy at mymymymy dot com [2015-01-02 09:41:59]

$children = $xml->children();
var_dump($children[0]["@attributes"]);//"NULL"
var_dump($children[0]);//(2) ["@attributes"]=>array(1) {['x']=> string(1) '2'}

no faithfully (not true)
------
example:

SimpleXMLElement Object
(
    [@attributes] => Array
        (
            [name] => USA
        )
)

print_r($xml->country->attributes()->name);
show:
SimpleXMLElement Object
(
    [0] => USA
)

print_r((string)$xml->country->attributes()->name);
show:
USA

[#3] RiKdnUA at mail dot ru [2013-12-02 21:40:45]

?????? ?????????? XML-?????????? ??????????? ??? UTF-8, ??????????? ?????????? ??????? ?????????? ?????? ?????? version='...' ?? ?????? standalone='...'. ????? ??????????? ?????????? XML.

If encoding XML-document differs from UTF-8. Encoding declaration should follow immediately after the version = '...' and before standalone = '...'. This requirement is standard XML.

<?phpxml version='1.0' encoding='windows-1251' standalone='yes'?>
Ok
<?phpxml version='1.0' standalone='yes' encoding='windows-1251'?>
<body>????????? ??????. Russian language</body>
Fatal error: Uncaught exception 'Exception' with message 'String could not be parsed as XML' in...

[#4] eng dot emad_2010 at yahoo dot com [2013-10-08 23:46:42]

Example #  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  .
The simplexml_import_dom() function returns a SimpleXMLElement object from a DOM node.
DOM         object

<?php //create DOM  document $dom that contain XML $dom = new DOMDocument; $dom->loadXML('<books><book><title>blah</title></book></books>'); if (!$dom) {     echo 'Error while parsing the document';     exit; } //convert DOM document $dom to object $books $books = simplexml_import_dom($dom); //access object $books echo $books->book[0]->title; ?>

[#5] jishcem at gmail dot com [2013-03-12 07:31:55]

For me it was easier to use arrays than objects,

So, I used this code,

$xml = simplexml_load_file('xml_file.xml');

$json_string = json_encode($xml);

$result_array = json_decode($json_string, TRUE);

Hope it would help someone

[#6] gkokmdam at zonnet dot nl [2011-02-23 13:54:24]

A quick tip on xpath queries and default namespaces. It looks like the XML-system behind SimpleXML has the same workings as I believe the XML-system .NET uses: when one needs to address something in the default namespace, one will have to declare the namespace using registerXPathNamespace and then use its prefix to address the otherwise in the default namespace living element.

<?php $string = <<<XML <?xml version='1.0'?>
<document xmlns="http://www.w3.org/2005/Atom">
<title>Forty What?</title>
<from>Joe</from>
<to>Jane</to>
<body>
I know that's the answer -- but what's the question?
</body>
</document>
XML;

$xml = simplexml_load_string($string);
$xml->registerXPathNamespace("def", "http://www.w3.org/2005/Atom");

$nodes = $xml->xpath("//def:document/def:title");

?>

[#7] kdos [2011-01-31 05:32:19]

Using stuff like: is_object($xml->module->admin) to check if there actually is a node called "admin", doesn't seem to work as expected, since simplexml always returns an object- in that case an empty one - even if a particular node does not exist.
For me good old empty() function seems to work just fine in such cases.

Cheers

[#8] Max K. [2010-06-20 14:38:58]

From the README file:

SimpleXML is meant to be an easy way to access XML data.

SimpleXML objects follow four basic rules:

1) properties denote element iterators
2) numeric indices denote elements
3) non numeric indices denote attributes
4) string conversion allows to access TEXT data

When iterating properties then the extension always iterates over
all nodes with that element name. Thus method children() must be
called to iterate over subnodes. But also doing the following:
foreach ($obj->node_name as $elem) {
// do something with $elem
}
always results in iteration of 'node_name' elements. So no further
check is needed to distinguish the number of nodes of that type.

When an elements TEXT data is being accessed through a property
then the result does not include the TEXT data of subelements.

Known issues
============

Due to engine problems it is currently not possible to access
a subelement by index 0: $object->property[0].

[#9] ie dot raymond at gmail dot com [2010-04-01 15:07:49]

If you need to output valid xml in your response, don't forget to set your header content type to xml in addition to echoing out the result of asXML():

<?php $xml=simplexml_load_file('...'); ... ...xml stuff ... //output xml in your response: header('Content-Type: text/xml'); echo $xml->asXML(); ?>

[#10] php at keith tyler dot com [2009-12-23 12:57:29]

[Editor's Note: The SimpleXMLIterator class, however, does implement these methods.]

While SimpleXMLElement claims to be iterable, it does not seem to implement the standard Iterator interface functions like ::next and ::reset properly. Therefore while foreach() works, functions like next(), current(), or each() don't seem to work as you would expect -- the pointer never seems to move or keeps getting reset.

[#11] bjorn at xQmail dot eu [2009-08-31 07:48:50]

If you're not sure the XML will be valid you'd better use:

<?php $xmlObject = simplexml_load_string($xml); // or $xmlObject = simplexml_load_file(xml); ?>

Both of these return a SimpleXMLElement Object or a libXMLError Object.

[#12] radams at circlepix com [2009-04-24 10:52:38]

To test whether an element exists:

<?php     $xml = <<<EOT <?xml version='1.0' standalone='yes'?>
<root>
    <test1></test1>
    <test2 />
    <test4> </test4>
</root>
EOT;

    $xmlDoc = new SimpleXMLElement($xml);

echo "Test1: \n";
var_dump($xmlDoc->test1);
echo "\n(" . (bool)$xmlDoc->test1 . ")";
echo "\n\n";

echo "Test2: \n";
var_dump($xmlDoc->test2);
echo "\n(" . (bool)$xmlDoc->test2 . ")";
echo "\n\n";

echo "Test3: \n";
var_dump($xmlDoc->test3);
echo "\n(" . (bool)$xmlDoc->test3 . ")";
echo "\n\n";

echo "Test4: \n";
var_dump($xmlDoc->test4);
echo "\n(" . (bool)$xmlDoc->test4 . ")";
echo "\n\n";

?>

The var_dumps for test1, test2, and test3 are identical, but the (bool) test gives a '1' for test1 and test2, and a '' for test3.