PHP | DOMNode lookupNamespaceUri() Function

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The DOMNode::lookupNamespaceUri() function is an inbuilt function in PHP which is used to get the namespace URI of the node based on the prefix.

Syntax:

string DOMNode::lookupNamespaceUri( string $prefix )

Parameters: This function accepts a single parameter $prefix which holds the prefix.

Return Value: This function returns namespace URI of the node.

Below examples illustrate the DOMNode::lookupNamespaceUri() function in PHP:

Example 1:

<?php 
  
// Create a new DOMDocument instance 
$document = new DOMDocument(); 
  
// Create a XML variable with no namespace 
$xml = <<<XML 
<?xml version="1.0" encoding="utf-8"?> 
<root> 
    <h1>zambiatek</h1> 
</root> 
XML; 
  
// Load the XML 
$document->loadXML($xml); 
  
// Get the default namespace URI 
$uri = $document->documentElement->lookupnamespaceURI(null); 
echo $uri; 
?> 

Output:

// Empty string which means no namespace is there.

Example 2:

<?php 
  
// Create a new DOMDocument instance 
$document = new DOMDocument(); 
  
// Load the XML with a namespace with prefix x 
$document->loadXML("<?xml version=\"1.0\"?> 
    <div xmlns:x=\"my_namespace\"> 
        <x:h1 x:style=\"color:red;\"> zambiatek </x:h1> 
    </div> 
"); 
  
// Get the URI with prefix x 
$uri = $document->documentElement->lookupnamespaceURI('x'); 
echo $uri; 
?> 