PHP | DOMXPath query() Function

0 0 1 minute read

The DOMXPath::query() function is an inbuilt function in PHP which is used to evaluate the given XPath expression.

Syntax:

DOMNodeList DOMXPath::query( string $expression, 
       DOMNode $contextnode, bool $registerNodeNS )

Parameters: This function accept three parameters as mentioned above and described below:

$expression: It specifies the XPath expression to execute.
$contextnode (Optional): It specifies the optional contextnode for doing relative XPath queries. By default, the queries are relative to the root element.
$registerNodeNS (Optional): It specifies the optional registerNodeNS to disable automatic registration of the context node.

Return Value: This function returns a DOMNodeList containing all nodes matching the given XPath expression. Any expression which does not return nodes will return an empty DOMNodeList.

Below given programs illustrate the DOMXPath::query() function in PHP:

Program 1: In this program we will fetch all the element values of elements with name content.

<?php 
  
// Create a new DOMDocument instance 
$document = new DOMDocument(); 
  
// Create a XML 
$xml = <<<XML 
<?xml version="1.0" encoding="utf-8"?> 
<root> 
    <content> 
        First 
    </content> 
    <content> 
        Second 
    </content> 
    <content> 
        Third 
    </content> 
</root> 
XML; 
  
// Load the XML 
$document->loadXML($xml); 
  
// Create a new DOMXPath instance 
$xpath = new DOMXPath($document); 
  
// Get the root element 
$tbody = $document->getElementsByTagName('root')->item(0); 
  
// Get all the element with name content 
$query = '//content'; 
  
// Execute the query 
$entries = $xpath->query($query); 
  
foreach ($entries as $entry) { 
    echo $entry->nodeValue . "<br>"; 
} 
?> 

Output:

First
Second
Third

Program 2: In this program we will count all the elements with name h1.

<?php 
// Create a new DOMDocument instance 
$document = new DOMDocument(); 
  
// Create a XML 
$xml = <<<XML 
<?xml version="1.0" encoding="utf-8"?> 
<root> 
    <h1> 
        Hello 
    </h1> 
    <h1> 
        World 
    </h1> 
    <h1> 
        Foo 
    </h1> 
    <h1> 
        Bar 
    </h1> 
</root> 
XML; 
  
// Load the XML 
$document->loadXML($xml); 
  
// Create a new DOMXPath instance 
$xpath = new DOMXPath($document); 
  
// Get the root element 
$tbody = $document->getElementsByTagName('root')->item(0); 
  
// Get all the element with name h1 
$query = '//h1'; 
  
// Execute the query 
$entries = $xpath->query($query); 
  
// Count the number of headings 
echo count($entries); 
?> 