How to : Create Attribute, Get Attribute & Check whether an Attribute Exists in XML File

Manipulating the nodes and the elements in an XML file is easy by using PHP code. We will see how to create an attribute for an element in an xml file and to get an attribute from an xml file. We will also use a function to check whether an attribute exists in an xml file.


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It is easy to do the above tasks by using the function like createAttribute, getAttributeNode, and hasAttribute.

Creating an Attribute

Consider an xml file candidate.xml as given below:

<?xml version="1.0" encoding="UTF-8"?>
<candidate>
<candidatename>Robert</candidatename>
<candidatecity>New York</candidatecity>
<SSN>20072007</SSN>
<organization>XYZ Corp</organization>
</candidate>

In the above xml file we will add an attribute named 'candidatedesignation' by using the function createAttribute.

The code to achieve this task is given below:

<?php
$xdoc = new DomDocument;
$xdoc->Load('C:/php/xml_files/candidate.xml');
$candidate = $xdoc->getElementsByTagName('candidate')->item(0);
$newattribute=$xdoc->createAttribute('candidatedesignation');
$candidate -> appendChild($newattribute);
$test = $xdoc->save("C:/php/xml_files/candidate2.xml");
echo "<B>Attribute Created<B>"
?>

If you check the new xml file you can find an attribute added in the candidate node as,

<?xml version="1.0" encoding="UTF-8"?>
<candidate candidatedesignation="">
...
...
</candidate>

Getting an Attribute

To get an attribute that is found in a node you can use the getAttribute function as given below. Consider an XML file candidate.xml that is given below:

<?xml version="1.0" encoding="UTF-8"?>
<candidate>
<candidatename id='candid'>Robert</candidatename>
<candidatecity>New York</candidatecity>
<SSN>20072007</SSN>
<organization>XYZ Corp</organization>
</candidate>
The code to get the attribute in the above file is given below. After getting the attribute it is echoed in the form an html file so that it is displayed in the browser.

<?php
$xdoc = new DomDocument;
$xdoc->Load('C:/php/xml_files/candidate.xml');
$candidatename = $xdoc->getElementsByTagName('candidatename')->item(0);
$attribNode = $candidatename->getAttributeNode('id');
echo "<HTML><Head>";
echo "<title> Getting Attribute Example</title>";
echo "</Head><body><B>";
echo "Attribute Name is :".$attribNode->name;
echo "<BR>Attribute Value is :".$attribNode->value;
echo "</B></body></HTML>";
?>

The output of the above code will be as shown in the figure below:

Checking whether an Attribute exists

You can use the hasAttribute function to check whether an attribute exists or not. The sample code given below illustrates that function.

Consider the same candidate.xml file given in the above example that has an attribute 'id' for the element 'candidatename'. We will check this file to see if it has the attribute using the function in PHP.

<?php
$xdoc = new DomDocument;
$xdoc->Load('C:/php/xml_files/candidate.xml');
$candidatename = $xdoc->getElementsByTagName('candidatename')->item(0);
echo "<HTML><Head>";
echo "<title>Checking Attribute Example</title>";
echo "</Head><body><B>";
if($candidatename ->hasAttribute('id')){
echo "Attribute value :".$candidatename->getAttribute('id');
}else{
echo "Attribute 'id' does not exist";
}
echo "</B></body></HTML>";
?>

The above code checks for the 'id' attribute. For this purpose we have used an 'if' condition. If that attribute exists then you will be displayed the value of that attribute in the browser, otherwise you will get a message stating that the attribute does not exist in the node checked.

The output of this code in given in the figure below:




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