Undoubtedly, one of the most common operations involved in the manipulation of XML documents is the creation of custom attributes that can be appended to one or more nodes. To perform this specific task, the DOM XML extension provides an intuitive method called “createAttribute(),” which can be used to dynamically build new attributes.

Before I show you a concrete example of how to use this specific method, you should be aware that once a new attribute has been created, it must be inserted into the pertinent XML document via the “appendChild()” method (or a similar one). As you’ll see in a moment, all of the attributes should be appended to the document tree, as it is done with regular nodes.

Having clarified this point, pay attention to the following example, which shows how to use the method in question to assign a few simple attributes to several nodes of an existing XML document.

// example on creating a new DOMDocument object and appending an attribute using the 'createAttribute()' method

$elements=array('element1'=>'Element 1','element2'=>'Element
2','element3'=>'Element 3','element4'=>'Element 4','element5'=>'Element
5','element6'=>'Element 6','element7'=>'Element 7','element8'=>'Element
8','element9'=>'Element 9','element10'=>'Element 10');

$dom=new DOMDocument('1.0','iso-8859-1');

$rootElement=$dom->createElement('rootnode','');

// insert the root element into the document

$dom->appendChild($rootElement);

// insert additional elements into the document

foreach($elements as $key=>$value){

$element=$dom->createElement($key,$value);

// create attribute

$attribute=$dom->createAttribute('customattribute');

// append attribute to element

$element->appendChild($attribute);

// append element to document

$rootElement->appendChild($element);

}

// tell the browser the output is XML via the 'Content-Type' HTTP header

header('Content-Type: text/xml');

// display DOM document

echo $dom->saveXML();

/* displays the following

<?xml version="1.0" encoding="iso-8859-1"?>

<rootnode>

<element1 customattribute="">Element 1</element1>

<element2 customattribute="">Element 2</element2>

<element3 customattribute="">Element 3</element3>

<element4 customattribute="">Element 4</element4>

<element5 customattribute="">Element 5</element5>

<element6 customattribute="">Element 6</element6>

<element7 customattribute="">Element 7</element7>

<element8 customattribute="">Element 8</element8>

<element9 customattribute="">Element 9</element9>

<element10 customattribute="">Element 10</element10>

</rootnode>

*/

As shown by the previous example, adding a custom attribute to different nodes of a given XML document is actually a no-brainer process that can be performed with minor effort. In this case, I used the “createAttribute()” method to construct the attribute in memory, and then insert it into the document tree via the pertinent “appendChild()” method.

Lastly, the recently-created document is outputted to the browser through the “saveXML()” method that I introduced in the preceding article of this series. It’s worthwhile to mention two things here: first, no specific values have been assigned to the respective attributes, and second, all of the child nodes in the above XML document are dynamically generated from a basic PHP array.

Of course, the structure of the previous XML document is rather incomplete, since its attributes don’t contain a specific value. However, don’t worry about this issue for the time being, since in upcoming articles of this series, I’ll be discussing how to do this in detail.

So far, so good, right? At this time, you've hopefully learned how to insert some custom attributes into an existing XML document by using the API of the DOM XML extension. So, where do we go from here? Good question. In the last section of this article, I’ll teach you how to insert CDATA sections into a given XML string.

However, to see how this will be done, you’ll have to read the next few lines. Just click on the link below.