WiP

src/Document.php

@@ -13,7 +13,7 @@
 use DOMXPath;
 use RuntimeException;
 use const PHP_VERSION;
-use function func_get_args, libxml_get_last_error, trim, version_compare;
+use function func_get_args, method_exists, libxml_get_last_error, trim, version_compare;
 
 /**
 * @method Attr|false createAttribute(string $localName)
@@ -85,6 +85,13 @@ public function query(string $expression, ?DOMNode $contextNode = null, bool $re
 		return $result;
 	}
 
+	public function isEqualNode(?DOMNode $otherNode): bool
+	{
+		return method_exists('DOMDocument', 'isEqualNode')
+		     ? parent::isEqualNode($otherNode)
+		     : NodeComparator::isEqualNode($this, $otherNode);
+	}
+
 	protected function getNodesNamespace(): string
 	{
 		$namespace = __NAMESPACE__;

tests/DocumentFragmentTest.php

@@ -83,4 +83,17 @@ public function testQuery()
 
 		$this->assertEquals('xx', $fragment->query('x')->item(0)->getAttribute('value'));
 	}
+
+	public function testIsEqualNode()
+	{
+		$dom = new Document;
+
+		$frag1 = $dom->createDocumentFragment();
+		$frag2 = $dom->createDocumentFragment();
+		$frag1->appendElement('x')->setAttribute('value', 'xx');
+		$frag2->appendElement('x')->setAttribute('value', 'xx');
+		$this->assertTrue($frag1->isEqualNode($frag2));
+		$frag2->appendElement('x');
+		$this->assertFalse($frag1->isEqualNode($frag2));
+	}
 }

tests/DocumentTest.php

@@ -127,4 +127,15 @@ public function testFirstOfError()
 
 		@$dom->firstOf('x x');
 	}
+
+	public function testIsEqualNode()
+	{
+		$dom1 = new Document;
+		$dom1->loadXML('<x foo="123"/>');
+		$dom2 = new Document;
+		$dom2->loadXML('<x foo="123"/>');
+		$this->assertTrue($dom1->isEqualNode($dom2));
+		$dom2->loadXML('<x/>');
+		$this->assertFalse($dom1->isEqualNode($dom2));
+	}
 }