kodie/Modify_HTML.php

## Modify_HTML.php
<?php
$html = '<article class="grid-item"><p>Hello World</p></article><article class="grid-item"><p>Goodbye World</p></article>';
$head = '<head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /></head>';

libxml_use_internal_errors(true);
$dom = new DOMDocument('1.0', 'utf-8');
$dom->loadHTML($head . $html);
$xpath = new DOMXPath($dom);

// Loop through all article.grid-item elements and add the "invisible" class to them
$nodes = $xpath->query("//article[contains(concat(' ', normalize-space(@class), ' '), ' grid-item ')]");
foreach($nodes as $node) {
  $class = $node->getAttribute('class');
  $class .= ' invisible';
  $node->setAttribute('class', $class);
}

$content = preg_replace('/<\/?(!doctype|html|head|meta|body)[^>]*>/im', '', $dom->saveHTML());
libxml_use_internal_errors(false);

echo $content;
?>
	<?php
	$html = '<article class="grid-item"><p>Hello World</p></article><article class="grid-item"><p>Goodbye World</p></article>';
	$head = '<head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /></head>';

	libxml_use_internal_errors(true);
	$dom = new DOMDocument('1.0', 'utf-8');
	$dom->loadHTML($head . $html);
	$xpath = new DOMXPath($dom);

	// Loop through all article.grid-item elements and add the "invisible" class to them
	$nodes = $xpath->query("//article[contains(concat(' ', normalize-space(@class), ' '), ' grid-item ')]");
	foreach($nodes as $node) {
	$class = $node->getAttribute('class');
	$class .= ' invisible';
	$node->setAttribute('class', $class);
	}

	$content = preg_replace('/<\/?(!doctype\|html\|head\|meta\|body)[^>]*>/im', '', $dom->saveHTML());
	libxml_use_internal_errors(false);

	echo $content;
	?>