How to get innerHTML of DOMNode?

Compare this updated variant with PHP Manual User Note #89718:

<?php 
function DOMinnerHTML(DOMNode $element) 
{ 
    $innerHTML = ""; 
    $children  = $element->childNodes;

    foreach ($children as $child) 
    { 
        $innerHTML .= $element->ownerDocument->saveHTML($child);
    }

    return $innerHTML; 
} 
?> 

Example:

<?php 
$dom= new DOMDocument(); 
$dom->preserveWhiteSpace = false;
$dom->formatOutput       = true;
$dom->load($html_string); 

$domTables = $dom->getElementsByTagName("table"); 

// Iterate over DOMNodeList (Implements Traversable)
foreach ($domTables as $table) 
{ 
    echo DOMinnerHTML($table); 
} 
?> 

In addition to trincot's nice version with array_map and implode but this time with array_reduce:

return array_reduce(
   iterator_to_array($node->childNodes),
   function ($carry, \DOMNode $child) {
        return $carry.$child->ownerDocument->saveHTML($child);
   }
);

Still don't understand, why there's no reduce() method which accepts arrays and iterators alike.

Here's another approach based on this comment by Drupella on php.net, that worked well for my project. It defines the innerHTML() by creating a new DOMDocument, importing and appending to it the target node, instead of explicitly iterating over child nodes.

InnerHTML

Let's define this helper function:

function innerHTML( \DOMNode $n, $include_target_tag = true ) {
  $doc = new \DOMDocument();
  $doc->appendChild( $doc->importNode( $n, true ) );
  $html = trim( $doc->saveHTML() );
  if ( $include_target_tag ) {
      return $html;
  }
  return preg_replace( '@^<' . $n->nodeName .'[^>]*>|</'. $n->nodeName .'>$@', '', $html );
}

where we can include/exclude the outer target tag through the second input argument.

Usage Example

Here we extract the inner HTML for a target tag given by the "first" id attribute:

$html = '<div id="first"><h1>Hello</h1></div><div id="second"><p>World!</p></div>';
$doc  = new \DOMDocument();
$doc->loadHTML( $html );
$node = $doc->getElementById( 'first' );

if ( $node instanceof \DOMNode ) {

    echo innerHTML( $node, true );
    // Output: <div id="first"><h1>Hello</h1></div>    

    echo innerHTML( $node, false );
    // Output: <h1>Hello</h1>
}

Live example:

http://sandbox.onlinephpfunctions.com/code/2714ea116aad9957c3c437d46134a1688e9133b8

Old query, but there is a built-in method to do that. Just pass the target node to DomDocument->saveHtml().

Full example:

$html = '<div><p>ciao questa è una <b>prova</b>.</p></div>';
$dom = new DomDocument($html);
@$dom->loadHTML($html);
$xpath = new DOMXPath($dom);
$node = $xpath->query('.//div/*'); // with * you get inner html without surrounding div tag; without * you get inner html with surrounding div tag
$innerHtml = $dom->saveHtml($node);
var_dump($innerHtml);

Output: <p>ciao questa è una <b>prova</b>.</p>

For people who want to get the HTML from XPath query, here is my version:

$xpath = new DOMXpath( $my_dom_object );

$DOMNodeList = $xpath->query('//div[contains(@class, "some_custom_class_in_html")]');

if( $DOMNodeList->count() > 0 ) {
    $page_html = $my_dom_object->saveHTML( $DOMNodeList->item(0) );
}