SimpleXMLElement::addAttribute

(PHP 5 >= 5.1.3, PHP 7, PHP 8)

SimpleXMLElement::addAttribute — Adds an attribute to the SimpleXML element

Description

public SimpleXMLElement::addAttribute(string $qualifiedName, string $value, ?string $namespace = null): void

Adds an attribute to the SimpleXML element.

Parameters

qualifiedName: The name of the attribute to add.
value: The value of the attribute.
namespace: If specified, the namespace to which the attribute belongs.

Return Values

No value is returned.

Examples

Note:
Listed examples may include example.php, which refers to the XML string found in the first example of the basic usage guide.

Example #1 Add attributes and children to a SimpleXML element

<?php

include 'example.php';
 
$sxe = new SimpleXMLElement($xmlstr);
$sxe->addAttribute('type', 'documentary');

$movie = $sxe->addChild('movie');
$movie->addChild('title', 'PHP2: More Parser Stories');
$movie->addChild('plot', 'This is all about the people who make it work.');

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

$rating = $movie->addChild('rating', '5');
$rating->addAttribute('type', 'stars');
 
echo $sxe->asXML();

?>

The above example will output something similar to:

<?xml version="1.0" standalone="yes"?>
<movies type="documentary">
 <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>
  </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>
 <movie>
  <title>PHP2: More Parser Stories</title>
  <plot>This is all about the people who make it work.</plot>
  <characters>
   <character>
    <name>Mr. Parser</name>
    <actor>John Doe</actor>
   </character>
  </characters>
  <rating type="stars">5</rating>
 </movie>
</movies>

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User Contributed Notes 7 notes

down

Patanjali ¶

8 years ago

You cannot use this to update an existing attribute's value.

Instead, get a DOM version of the SimpleXMLElement and use setAttribute, as per:

$XML = '<element a="aa">Text</element>';
$snode = new simple_xml_element($XML);

$dnode = dom_import_simplexml($snode);
$dnode->setAttribute('a', 'bb');

Resulting XML for the node is:
<element a="bb">Text</element>

down

booleer at yahoo dot it ¶

13 years ago

If the attribute already exists, addAttribute does nothing.

example:
<?php
$xml_string = <<<XML
<?xml version="1.0" encoding="UTF-8"?>
<root>
   <item id="foo">
<root>
XML;

$xml = simplexml_load_string($xml_string);
$xml->item->addAttribute('id', 'bar');
echo $xml->asXML();
?>

The above examples will output:
<?xml version="1.0" encoding="UTF-8"?>
<root>
   <item id="foo">
<root>

down

caffeinatedbits ¶

1 year ago

Just found another gem. Need to remove an attribute? That's simple too!

<?php

$xml = <<<EOF
<?xml version="1.0" encoding="utf-8" ?>
<Animals>
    <Dog breed="chihuahua"/>
</Animals>
EOF;

$animals = new SimpleXMLElement($xml);

echo $animals->Dog->asXML();
// <Dog breed="chihuahua"/>

unset($animals->Dog['breed']);

echo $animals->Dog->asXML();
// <Dog/>

?>

down

caffeinatedbits ¶

1 year ago

I needed a way to update an attribute, but I could not find any documented way to do this.

After much experimentation, here's my findings of what works - the answer was so simple it took me 8 tries to figure it out :-)

Given the following example:

<?php

$xml = <<<EOF
<?xml version="1.0" encoding="utf-8" ?>
<Animals>
    <Dog/>
</Animals>
EOF;

$animals = new SimpleXMLElement($xml);

echo $animals->Dog->asXML();
// <Dog/>

?>

Test #6 - maybe directly modifying the attributes() Iterator like an array will secretly call __set() magic method?

TL;DR: yep

<?php

...

$animals->Dog->addAttribute('breed', "chihuahua");

echo $animals->Dog->asXML();
// <Dog breed="chihuahua">

$dogAttrs = $animals->Dog->attributes();
// object(SimpleXMLElement)#4 (1) {
// ["@attributes"]=>
//   array(1) {
//     ["breed"]=>
//     string(9) "chihuahua"
//   }
// }

$dogAttrs['breed'] = "poodle";
// works!

echo $animals->Dog->asXML();
// <Dog breed="poodle">

?>

Test #7 - maybe I don't even need to call attributes() at all?

TL;DR: I sure don't!

<?php

...

$animals->Dog->addAttribute('breed', "chihuahua");

echo $animals->Dog->asXML();
// <Dog breed="chihuahua">

$animals->Dog['breed'] = "poodle";
// works!

echo $animals->Dog->asXML();
// <Dog breed="poodle">

?>

Test #8 - Maybe I never needed to call addAttribute() in the first place?

TL;DR: nope, I can skip that altogether!

<?php

...

$animals->Dog['breed'] = "chihuahua";
// works!

echo $animals->Dog->asXML();
// <Dog breed="chihuahua">

$animals->Dog['breed'] = "poodle";
// works!

echo $animals->Dog->asXML();
// <Dog breed="poodle">

?>

FYI: I also submitted another separate note with what does NOT work just in case you, like me, are curious and tempted to try another way.

down

p.servus ¶

13 years ago

If you need an Namespace, you must write a Prefix of the Namespace + the Name of the Attribute ("prefix:name") as the first parameter AND the uri as the third one. (I don't know why?!)

Example code:
<?php
$xml = new SimpleXMLElement("<packagedElement></packagedElement>");
$xml->addAttribute("xmi:type", "uml:Class", "http://schema.omg.org/spec/XMI/2.1"); 
echo $xml->asXml();
?>

Output:
<packagedElement xmlns:xmi="http://schema.omg.org/spec/XMI/2.1" xmi:type="uml:Class"></packagedElement>

down

caffeinatedbits ¶

1 year ago

I needed a way to update an attribute, but I could not find any documented way to do this.

TL;DR: It's not only possible, but unbelievably simple. See the other note I submitted for what actually works (sorry, I could not fit it all in a single note due to the 4095 character limit).

After much experimentation, here's my findings of what does NOT work; hopefully, it saves you the time and frustration it cost me.

Given the following example:

<?php

$xml = <<<EOF
<?xml version="1.0" encoding="utf-8" ?>
<Animals>
    <Dog/>
</Animals>
EOF;

$animals = new SimpleXMLElement($xml);

echo $animals->Dog->asXML();
// <Dog/>

?>

Test #1 - attempt to call addAttribute() twice

TL;DR: PHP Warning: SimpleXMLElement::addAttribute(): Attribute already exists

<?php

...

$animals->Dog->addAttribute('breed', "chihuahua");

echo $animals->Dog->asXML();
// <Dog breed="chihuahua"/>

$animals->Dog->addAttribute('breed', "poodle");
// PHP Warning: SimpleXMLElement::addAttribute(): Attribute already exists

echo $animals->Dog->asXML();
// <Dog breed="chihuahua"/>

?>

Test #2 - attempt to iterate attributes() (an Iterator) by reference

TL;DR: An iterator cannot be used with foreach by reference

<?php

...

$animals->Dog->addAttribute('breed', "chihuahua");

echo $animals->Dog->asXML();
// <Dog breed="chihuahua">

try {
    foreach ($animals->Dog->attributes() as $attr => &$value) {
        if ("breed" === $attr) {
            $value = "poodle";
        }
    }
} catch (Throwable $e) {
    echo $e->getMessage();
    // An iterator cannot be used with foreach by reference
}

echo $animals->Dog->asXML();
// <Dog breed="chihuahua">

?>

Test #3 - attempt to re-parse child element and then call addAttribute() on the newly parsed element, as suggested in a note I found here

TL;DR: PHP Warning: SimpleXMLElement::addAttribute(): Attribute already exists

<?php

...

$animals->Dog->addAttribute('breed', "chihuahua");

echo $animals->Dog->asXML();
// <Dog breed="chihuahua">

$animals->Dog = new SimpleXMLElement($animals->asXML());

$animals->Dog->addAttribute('breed', "poodle");
// PHP Warning: SimpleXMLElement::addAttribute(): Attribute already exists

echo $animals->Dog->asXML();
// <Dog breed="chihuahua">

?>

Test #4 - attempt to modify @attributes array element

TL;DR: PHP Notice:  Indirect modification of overloaded element of SimpleXMLElement has no effect

<?php

...

$animals->Dog->addAttribute('breed', "chihuahua");

echo $animals->Dog->asXML();
// <Dog breed="chihuahua">

$dogAttrs = $animals->Dog->attributes();
// object(SimpleXMLElement)#4 (1) {
// ["@attributes"]=>
//   array(1) {
//     ["breed"]=>
//     string(9) "chihuahua"
//   }
// }

$dogAttrs['@attributes']['breed'] = "poodle";
// PHP Notice:  Indirect modification of overloaded element of SimpleXMLElement has no effect

echo $animals->Dog->asXML();
// <Dog breed="chihuahua">

?>

Test #5 - cast attributes() to array and set value of 'breed' element

TL;DR: does not update value in original object

<?php

...

$animals->Dog->addAttribute('breed', "chihuahua");

echo $animals->Dog->asXML();
// <Dog breed="chihuahua">

$dogAttrs = (array) $animals->Dog->attributes();
// array(1) {
//     ["@attributes"]=>
//   array(1) {
//         ["breed"]=>
//     string(9) "chihuahua"
//   }
// }

$dogAttrs['@attributes']['breed'] = "poodle";

echo $animals->Dog->asXML();
// <Dog breed="chihuahua">

?>

down

sarlak ¶

13 years ago

You can access a node child with his name this way :

<?php
$root = new SimpleXMLElement($filePath);
echo $root->nodeName->attributes;

// It works recursivly so this will work too
echo $root->nodeName->subNodeName->attributes();
?>

But if you want to ADD an attribute to a children you MUST use the children() method to access and modfiy it or it will modify the parent's attributes.

<?php
// Add a subnode
$element->nodeName->addChild('subNodeName', "whatever you want");
                
// Get the pos in the childrens of the parent node
$lastNodePos = $element->nodeName->count()-1;

// Get the parents node childrens
$nodeChildrens = $element->nodeName->children();

// Add an attribute to the last created
$nodeChildrens[$lastNodePos]->addAttribute('attributeName', "The attribute value);
?>

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SimpleXMLElement::addAttribute

Description

Parameters

Return Values

Examples

See Also

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User Contributed Notes 7 notes