The SimpleXMLElement class

(PHP 5 >= 5.0.1, PHP 7)

Introduction

Represents an element in an XML document.

Class synopsis

SimpleXMLElement implements Traversable {

/* Methods */

final public __construct ( string $data [, int $options = 0 [, bool $data_is_url = false [, string $ns = "" [, bool $is_prefix = false ]]]] )

public void addAttribute ( string $name [, string $value [, string $namespace ]] )

public SimpleXMLElement addChild ( string $name [, string $value [, string $namespace ]] )

public mixed asXML ([ string $filename ] )

public SimpleXMLElement attributes ([ string $ns = NULL [, bool $is_prefix = false ]] )

public SimpleXMLElement children ([ string $ns [, bool $is_prefix = false ]] )

public int count ( void )

public array getDocNamespaces ([ bool $recursive = false [, bool $from_root = true ]] )

public string getName ( void )

public array getNamespaces ([ bool $recursive = false ] )

public bool registerXPathNamespace ( string $prefix , string $ns )

public string __toString ( void )

public array xpath ( string $path )

}

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 — Alias of SimpleXMLElement::asXML
SimpleXMLElement::__toString — Returns the string content
SimpleXMLElement::xpath — Runs XPath query on XML data

User Contributed Notes

rmirabelle

5 years ago


To further previous comments and drive the point home:

What makes SimpleXMLElement tricky to work with is that it feels and behaves like an object, but is actually a system RESOURCE,  (specifically a libxml resource).  

That's why you can't store a SimpleXMLElement to $_SESSION or perform straight comparison operations on node values without first casting them to some type of object.  $_SESSION expects to store 'an object' and comparison operators expect to compare 2 'objects' and SimpleXMLElements are not objects.  

When you echo or print a node's value, PHP converts the value (a resource) into a string object for you.  It's a time saver for sure, but can fool you into thinking that your SimpleXMLElement is an object.  

Hope this helps clarify

juanfhj at gmail dot spam dot me dot not dot com

4 years ago


To access the underlying element as a string, it's necessary to make the cast $x = (string)$my_xml_element.

Anonymous

4 years ago


Warning to anyone trying to parse XML with a key name that includes a hyphen ie.)
<subscribe>
    <callback-url>example url</callback-url>
</subscribe>

In order to access the callback-url you will need to do something like the following:
<?php
$xml = simplexml_load_string($input);
$callback = $xml->{"callback-url"};
?>
If you attempt to do it without the curly braces and quotes you will find out that you are returned a 0 instead of what you want.

heaver

3 years ago


XML to JSON conversion without '@attributes'
<?php
function XML2JSON($xml) {

        function normalizeSimpleXML($obj, &$result) {
            $data = $obj;
            if (is_object($data)) {
                $data = get_object_vars($data);
            }
            if (is_array($data)) {
                foreach ($data as $key => $value) {
                    $res = null;
                    normalizeSimpleXML($value, $res);
                    if (($key == '@attributes') && ($key)) {
                        $result = $res;
                    } else {
                        $result[$key] = $res;
                    }
                }
            } else {
                $result = $data;
            }
        }
        normalizeSimpleXML(simplexml_load_string($xml), $result);
        return json_encode($result);
    }
?>

cherubangel at gmail dot com

5 years ago


Note that changing attributes from within a foreach loop, especially namespaced attributes, can be very tricky.

For example, when trying to change the value of an existing xlink:href attribute:
<?php
foreach($xmlelement -> attributes('xlink', true) as $attribute => $attribvalue){
    $attribvalue[0] = 'value'; // Throws an error
    $attribvalue = 'value'; // Does not change your XML
    $xmlelement -> addAttribute($attribute, 'value', 'http://www.w3.org/1999/xlink'); // Adds an attribute, does not change existing one.
    $xmlelement[$attribute] = 'value'; // Adds an attribute, does not change existing one.
}
?>

Instead, you should access the array returned by the attributes() function directly, like this:
<?php
    $xmlelement -> attributes('xlink', true) -> href = 'value'; // Works!
?>

saganmarketing.com

4 years ago


Parsing an invalid XML string through SimpleXML causes the script to crash completely (usually) therefore it is best to make sure the XML is valid before parsing with something like this:

// Must be tested with ===, as in if(isXML($xml) === true){}
// Returns the error message on improper XML
function isXML($xml){
    libxml_use_internal_errors(true);

    $doc = new DOMDocument('1.0', 'utf-8');
    $doc->loadXML($xml);

    $errors = libxml_get_errors();

    if(empty($errors)){
        return true;
    }

    $error = $errors[0];
    if($error->level < 3){
        return true;
    }

    $explodedxml = explode("r", $xml);
    $badxml = $explodedxml[($error->line)-1];

    $message = $error->message . ' at line ' . $error->line . '. Bad XML: ' . htmlentities($badxml);
    return $message;
}

ms dot n at 163 dot com

5 years ago


Adds a new function for SimpleXMLElement class, in order to output HTML code.



<?php

class CeiXML extends SimpleXMLElement{

public function asHTML(){

$ele=dom_import_simplexml($this);

$dom = new DOMDocument('1.0', 'utf-8');

$element=$dom->importNode($ele,true);

$dom->appendChild($element);

return $dom->saveHTML();

}

}

?>

frame at dynamiccreated dot de

2 years ago


Important note I miss here in the documentation:

SimpleXML supports Array/Iteration-Methods. Therefore it is possible to 

add attributes
edit attributes
remove attributes

add nodes
edit nodes
remove nodes

This is the reason why SimpleXML provides only add-methods not deleting- or editing-methods. We also need this methods because SimpleXML acts as a normal class and
new member will not converted to a new node.

Deleting a node seems not to be possible within a foreach-loop. The reason is simple. To do that we need a valid key, but the Iterator only gives us a "understandable feedback" on which node we are working on: the tag name.

So this will not work:

<?php
foreach($doc->seg as $key => $seg)
{
    if((string)$seg['id'] === 'whatever')
    {
        unset($seg); // only clears local copy
        unset($seg[$key]); // wrong index "seg"
    }
}
?>

But this, eg. will work:
<?php
unset($doc->seg[2]);
?>

In case of doubt always do a print_r/var_dump(). It nicely shows the real linked indexes.

Yukull

3 years ago


xml to object conversion function :
<?php
/**
    @param:
        $xml: SimpleXMLElement
        $force: set to true to always create 'text', 'attribute', and 'children' even if empty
    @return
        object with attributs:
            (string) name: XML tag name
            (string) text: text content of the attribut name
            (array) attributes: array witch keys are attribute key and values are attribute value
            (array) children: array of objects made with xml2obj() on each child
**/
function xml2obj($xml,$force = false){

    $obj = new StdClass();    

    $obj->name = $xml->getName();
    
    $text = trim((string)$xml);
    $attributes = array();
    $children = array();
    
    foreach($xml->attributes() as $k => $v){
        $attributes[$k]  = (string)$v;
    }
    
    foreach($xml->children() as $k => $v){
        $children[] = xml2obj($v,$force);
    }
    
    
    if($force or $text !== '')
        $obj->text = $text;
        
    if($force or count($attributes) > 0)
        $obj->attributes = $attributes;
        
    if($force or count($children) > 0)
        $obj->children = $children;
        
        
    return $obj;
}
?>

demian dot katz at villanova dot edu

4 years ago


Here is a more namespace-aware version of the earlier function for attaching one SimpleXMLElement to another.  I'm sure it could still be further improved (right now it generates some redundant xmlns definitions), but it seems to be working well enough for my purposes so far.

function SimpleXMLElement_append($parent, $child)
{
    // get all namespaces for document
    $namespaces = $child->getNamespaces(true);

    // check if there is a default namespace for the current node
    $currentNs = $child->getNamespaces();
    $defaultNs = count($currentNs) > 0 ? current($currentNs) : null;
    $prefix = (count($currentNs) > 0) ? current(array_keys($currentNs)) : '';
    $childName = strlen($prefix) > 1
        ? $prefix . ':' . $child->getName() : $child->getName();

    // check if the value is string value / data
    if (trim((string) $child) == '') {
        $element = $parent->addChild($childName, null, $defaultNs);
    } else {
        $element = $parent->addChild(
            $childName, htmlspecialchars((string)$child), $defaultNs
        );
    }

    foreach ($child->attributes() as $attKey => $attValue) {
        $element->addAttribute($attKey, $attValue);
    }
    foreach ($namespaces as $nskey => $nsurl) {
        foreach ($child->attributes($nsurl) as $attKey => $attValue) {
            $element->addAttribute($nskey . ':' . $attKey, $attValue, $nsurl);
        }
    }

    // add children -- try with namespaces first, but default to all children
    // if no namespaced children are found.
    $children = 0;
    foreach ($namespaces as $nskey => $nsurl) {
        foreach ($child->children($nsurl) as $currChild) {
            SimpleXMLElement_append($element, $currChild);
            $children++;
        }
    }
    if ($children == 0) {
        foreach ($child->children() as $currChild) {
            SimpleXMLElement_append($element, $currChild);
        }
    }
}

php at keith tyler dot com

6 years ago


The root node element of your input XML string is not retrievable as a property.

<?php
$xml="<foo>bar</foo>";
$sxe=new SimpleXMLElement($xml);
print $sxe->foo;
?>

prints nothing. You can only get to the root element via the array index method ($sxe[0]).

Also, you may not have two (or more) root elements -- that is apparently not well-formed XML.

<?php
$xml="<foo/><bar/>";
$sxe=new SimpleXMLElement($xml);
?>

throws an exception. A Q&D is to append an arbitraty root node structure to both ends of the input:

<?php
$xml="<foo/><bar/>";
$sxe=new SimpleXMLElement("<z>".$xml."</z>");
?>

Doing this also solves the above problem of root node property accessibility. (It may not work if your XML string includes a declaration.)

triplepoint at gmail dot com

6 years ago


It's occasionally useful to add an XML processing instruction to a SimpleXMLElement (treating it as if it were a full document).

<?php

class SimpleXMLElement_Plus extends SimpleXMLElement {



    public function addProcessingInstruction( $name, $value )

    {

        // Create a DomElement from this simpleXML object

        $dom_sxe = dom_import_simplexml($this);

        

        // Create a handle to the owner doc of this xml

        $dom_parent = $dom_sxe->ownerDocument;

        

        // Find the topmost element of the domDocument

        $xpath = new DOMXPath($dom_parent);

        $first_element = $xpath->evaluate('/*[1]')->item(0);

        

        // Add the processing instruction before the topmost element            

        $pi = $dom_parent->createProcessingInstruction($name, $value);

        $dom_parent->insertBefore($pi, $first_element);

    }

}

?>



For example, if you had a simpleXMLElement_Plus object made out of the xml fragment:

<xml><content /></xml>



And you needed the output to be:

<?xml version="1.0"?>

<?xml-stylesheet type="text/xsl" href="xsl/xsl.xsl"?>

<xml><content/></xml>



you could do (using the class above):

<?php

$xml = new SimpleXMLElement_Plus('<xml><content /></xml>');

$xml->addProcessingInstruction('xml-stylesheet', 'type="text/xsl" href="xsl/xsl.xsl"');

echo $xml->asXML();

?>

brett at brettbrewer dot com

6 years ago


Figuring out how to access the properties of a SimpleXmlElement object was a little tricky for me. In particular, it took a while to discover that I needed to cast my SimpleXmlElement properties to be of type "string" to print them or do comparisons on them. For instance, assuming you already have a string of xml in $xmlstr...

<?php
$sxml= new SimpleXmlElement($xmlstr);

if ((string) $sxml->property== "somevalue") {
    echo (string) $sxml->property;
}
?>
The properties of a SimpleXmlElement object are objects themselves, so you need to put "(string)" before them, which casts their values to a string instead of an object. I assume if you were doing a numeric comparison you'd want to cast to an (int) or something numeric instead.

francs at seznam dot cz

5 years ago


Be aware when you trying to cast some attribute to boolean.

(boolean)$xml->attributes()->someAtt;

returns TRUE if attribute is array([0] => 0);

use (boolean)(int) instead.

ivandosreisandrade at gmail dot com

6 years ago


Hello,

here goes my contribution for those whom are struggling to understand how SimpleXMLElement works.

After some time trying to figure out how this works, I've came up to this small example:

<?php
    $xmlstr = "<?xml version='1.0' ?>\n".
              // optionally you can specify a xml-stylesheet for presenting the results. just uncoment the following line and change the stylesheet name.
              /* "<?xml-stylesheet type='text/xsl' href='xml_style.xsl' ?>\n". */
              "<book></book>";

    // create the SimpleXMLElement object with an empty <book> element
    $xml = new SimpleXMLElement($xmlstr);

    // add some child nodes
    $xml->addChild("title", "Title of my book");
    $xml->addChild("abstract", "My book is about learning to work with SimpleXMLElement");

    // add some more child nodes
    $chapter1 = $xml->addChild("chapter_1");
    // add an attribute to child chapter_1
    $chapter1->addAttribute("chapter_title", "Introduction to my book");

    $chapter2 = $xml->addChild("chapter_2");
    $chapter2->addAttribute("chapter_title", "Development of my book");

    $chapter3 = $xml->addChild("chapter_3");
    $chapter3->addAttribute("chapter_title", "Another chapter of my book");

    $conclusion = $xml->addChild("conclusion", "The ending of my book");

    // insert the header to tell the browser how to read the document
    header("Content-type: text/xml");
    // print the SimpleXMLElement as a XML well-formed string
    echo $xml->asXML();
?>

With this script you can just copy-paste and try to understand how it works.
I hope it can help somebody :)

joshduck at gmail dot com

5 years ago


You should cast elements to a float (or even string) if you plan on using them in addition, multiplication, etc. If you don't then PHP will incorrectly treat the node values as an integer.

<?php
$obj = new SimpleXMLElement('<root>
    <a>1.9</a>
    <b>1.9</b>
</root>');

var_dump($obj->a + $obj->b);
var_dump((float)$obj->a + (float)$obj->b);
var_dump((string)$obj->a + (string)$obj->b);
?>

The first line gives: int(2)
The second and third give the expected result: float(3.8)

kweij at lsg dot nl

5 years ago


I'm using SimpleXML for, ofcourse, it's simplicity, however I did wanted to manipulate the xml and combining one SimpleXMLElement with any other, so I wrote this function to add a SimpleXMLElement-child.

<?php
function SimpleXMLElement_append($key, $value) {
    // check class
    if ((get_class($key) == 'SimpleXMLElement') && (get_class($value) == 'SimpleXMLElement')) {
        // check if the value is string value / data
        if (trim((string) $value) == '') {
            // add element and attributes
            $element = $key->addChild($value->getName());
            foreach ($value->attributes() as $attKey => $attValue) {
                $element->addAttribute($attKey, $attValue);
            }
            // add children
            foreach ($value->children() as $child) {
                SimpleXMLElement_append($element, $child);
            }
        } else {
            // set the value of this item
            $element = $key->addChild($value->getName(), trim((string) $value));
        }
    } else {
        // throw an error
        throw new Exception('Wrong type of input parameters, expected SimpleXMLElement');
    }
}
?>

I'd recommend SimpleXMLElement to extend it's addChild() function with the functionalitity above.

Pavel Musil pavel dot musil at gmail dot com

5 years ago


Simple recursive function to append XML object into SimpleXMLElement node:

<?php
// root: parent element - SimpleXMLElement instance
// append: XML object from simplexml_load_string

function xml_join($root, $append) {
    if ($append) {
        if (strlen(trim((string) $append))==0) {
            $xml = $root->addChild($append->getName());
            foreach($append->children() as $child) {
                xml_join($xml, $child);
            }
        } else {
            $xml = $root->addChild($append->getName(), (string) $append);
        }
        foreach($append->attributes() as $n => $v) {
            $xml->addAttribute($n, $v);
        }
    }
}

$xml_append = simplexml_load_string('<data><items><item id="1">value</item></items></data>');
$xml_root = new SimpleXMLElement('<result></result>');

$cxml = $xml_root->addChild('clone');
xml_join($cxml, $xml_append->items->item[0]);

print $xml_root->asXML();
?>

Result:
<?xml version="1.0"?>
<result>
    <clone>
        <item id="1">
            value
        </item>
    </clone>
</result>

dans at dansheps dot com

5 years ago


I created a little function to parse the simple XML into a structure which is easier to iterate(I believe anyways) than the simpleXML node structure.

<?php
function parseSimpleXML($xmldata)
    {
        $childNames = array();
        $children = array();

        if( $xmldata->count() !== 0 )
        {
            foreach( $xmldata->children() AS $child )
            {
                $name = $child->getName();

                if( !isset($childNames[$name]) )
                {
                    $childNames[$name] = 0;
                }

                $childNames[$name]++;
                $children[$name][] = $this->parseSimpleXML($child);
            }
        }

        $returndata = new XMLNode();
        if( $xmldata->attributes()->count() > 0 )
        {
            $returndata->{'@attributes'} = new XMLAttribute();
            foreach( $xmldata->attributes() AS $name => $attrib )
            {
                $returndata->{'@attributes'}->{$name} = (string)$attrib;
            }
        }

        if( count($childNames) > 0 )
        {
            foreach( $childNames AS $name => $count )
            {
                if( $count === 1 )
                {
                    $returndata->{$name} = $children[$name][0];
                }
                else
                {
                    $returndata->{$name} = new XMLMultiNode();
                    $counter = 0;
                    foreach( $children[$name] AS $data )
                    {
                        $returndata->{$name}->{$counter} = $data;
                        $counter++;
                    }
                }
            }
        }
        else
        {
            if( (string)$xmldata !== '' )
            {
                $returndata->{'@innerXML'} = (string)$xmldata;
            }
        }
        return $returndata;
    }
?>

The SimpleXMLElement class

Introduction

Class synopsis

Table of Contents

User Contributed Notes