Handling XML in PHP - II

If we want to generate XML in an organized way, we better use DOM extensions that comes with PHP. This creates DOMDocument object and the corresponding methods follow a pattern of adding, removing or manipulating elements and text nodes or adding attributes to DOM elements. The methods are quite similar to JavaScript DOM handling functions. 

Our first example loads an XML document using PHP DOM extension, then renders it on browser.

<?php
// Create new object
$xml_doc = new DOMDocument();
// Use load() method to load a document
$xml_doc->load('test.xml');
//Render it on screen
echo $xml_doc->saveXML();
?>

The content of test.xml is shown as output but only the text nodes. Tags are not shown. We need to view the source to get the actual XML structure. To render the whole XML structure on browser (without viewing the source), we need to include the header call : header('Content-type:text/xml'); before calling the saveXML() method.

Our next example, creates an XML document on the fly. Let's check it out.

<?php
header('Content-type:text/xml');

// Create new DOM object
$xml_doc = new DOMDocument();

// Add the root element 'students'
$students = $xml_doc->createElement('students');

// Append the new node to the doc
$xml_doc->appendChild($students);

// Now create First student Node
$student1 = $xml_doc->createElement('student');

// Create some attributes for student node
$attr1 = $xml_doc->createAttribute('id');
$attr1->value = "1";
$attr2 = $xml_doc->createAttribute('section');
$attr2->value = "A";
$attr3 = $xml_doc->createAttribute('username');
$attr3->value = "john_smith";

// Append the new attributes to the created element 'student'
$student1->appendChild($attr1);
$student1->appendChild($attr2);
$student1->appendChild($attr3);

// Now Insert a comment Node
$comm1 = $xml_doc->createComment('Teacher : Niel Hertz');
$student1->appendChild($comm1);

// Now Insert other child elements under "student" node
$fname = $xml_doc->createElement('fname');
$textNode = $xml_doc->createTextNode('John');
$fname->appendChild($textNode);

$lname = $xml_doc->createElement('lname');
$textNode = $xml_doc->createTextNode('Smith');
$lname->appendChild($textNode);

$roll_no = $xml_doc->createElement('roll_no');
$textNode = $xml_doc->createTextNode('109');
$roll_no->appendChild($textNode);

// Append all child nodes to 'student' node
$student1->appendChild($fname);
$student1->appendChild($lname);
$student1->appendChild($roll_no);

// Finally Append the 'student' node to 'students'
$students->appendChild($student1);

// Render it on screen
echo $xml_doc->saveXML();
?>

The above code generates and renders the following XML on the browser : 

<students>
 <student id="1" section="A" username="john_smith">
   <!--Teacher : Niel Hertz-->
   <fname>John109</fname>
   <lname>Smith</lname>
   <roll_no>109</roll_no>
 </student>
</students>

In the above code, we are using a DOMDocument object first, then using functions like createElement(), createAttribute(), createComment(), createTextNode() etc to create a DOM structure under it. All the created elements, attributes, comments, text nodes do not get into picture until we give calls to appendChild(). This function adds the element [or attribute etc] to its parent.

Next, we would parse an XML structure using the DOMDocument objects. Let's check out a program which loads an XML file and prints every elements and its contents on the screen.

<?php

// Create new DOM object
$xml_doc = new DOMDocument();

// Load external XML file

//$xml_doc->load('test.xml');  /// This is also OK
$xml_doc->loadXML(file_get_contents('test.xml'));

/// Get all the student element
$students = $xml_doc->getElementsByTagName('student');

//// Iterate thru each student node
foreach( $students as $stu )
{
  // Get Attributes of an element
  $id = $stu->getAttribute('id');
  $section = $stu->getAttribute('section');
  $username = $stu->getAttribute('username');
  
  // GET Child Elements/nodes and their values
  // A NodeList is returned by getElementsByTagName
  $nodes = $stu->getElementsByTagName('fname');
  $fname= $nodes->item(0)->nodeValue;

  $nodes = $stu->getElementsByTagName('lname');
  $lname= $nodes->item(0)->nodeValue;
  
  $nodes = $stu->getElementsByTagName('roll_no');
  $roll_no= $nodes->item(0)->nodeValue;
  
  $nodes = $stu->getElementsByTagName('class');
  $class= $nodes->item(0)->nodeValue;

  $nodes = $stu->getElementsByTagName('nickname');
  $nickname= $nodes->item(0)->nodeValue;


  /// Print on screen
  echo "<b>Student Details ::: </b><br>";
  echo "Name : $fname $lname [NickName : $nickname]<br>";
  echo "ID : $id, Section : $section, Class : $class<br>";
  echo "Username : $username<br><br>";
  
}

?>

The above program loads content of an XML file, then parses it and prints the student details. The functions like getElementsByTagName(), getElementById() locates elements within the XML document. The function getElementsByTagName() returns DOMNodeList class object holding all the elements found. Then we can simply use the item() method to access each element. Attributes of elements can be retrieved using getAttribute() method.

Check out the first part - Handling XML in PHP - I