diff --git a/NEWS b/NEWS
index 811eeb187dd6e..54ebe4b5e52e7 100644
--- a/NEWS
+++ b/NEWS
@@ -6,4 +6,7 @@ Core:
   . Fixed bug GH-12073 (Segfault when freeing incompletely initialized
     closures). (ilutov)
 
+DOM:
+  . Added DOMNode::compareDocumentPosition(). (nielsdos)
+
 <<< NOTE: Insert NEWS from last stable release here prior to actual release! >>>
diff --git a/UPGRADING b/UPGRADING
index 738c11675a902..73f50ea5d87d6 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -19,10 +19,25 @@ PHP 8.4 UPGRADE NOTES
 1. Backward Incompatible Changes
 ========================================
 
+- DOM:
+  . New methods and constants were added to some DOM classes. If you inherit
+    from these and you happen to have a method or property with the same name,
+    you might encounter errors if the declaration is incompatible.
+    Consult sections 2. New Features and 6. New Functions for a list of
+    newly implemented methods and constants.
+
 ========================================
 2. New Features
 ========================================
 
+- DOM:
+  . Added constant DOMNode::DOCUMENT_POSITION_DISCONNECTED.
+  . Added constant DOMNode::DOCUMENT_POSITION_PRECEDING.
+  . Added constant DOMNode::DOCUMENT_POSITION_FOLLOWING.
+  . Added constant DOMNode::DOCUMENT_POSITION_CONTAINS.
+  . Added constant DOMNode::DOCUMENT_POSITION_CONTAINED_BY.
+  . Added constant DOMNode::DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC.
+
 ========================================
 3. Changes in SAPI modules
 ========================================
@@ -39,6 +54,9 @@ PHP 8.4 UPGRADE NOTES
 6. New Functions
 ========================================
 
+- DOM:
+  . Added DOMNode::compareDocumentPosition().
+
 ========================================
 7. New Classes and Interfaces
 ========================================
diff --git a/ext/dom/node.c b/ext/dom/node.c
index 7064fa10f0e41..144181c67915e 100644
--- a/ext/dom/node.c
+++ b/ext/dom/node.c
@@ -1518,6 +1518,15 @@ static bool php_dom_node_is_equal_node(const xmlNode *this, const xmlNode *other
 PHP_DOM_DEFINE_LIST_EQUALITY_HELPER(xmlNode)
 PHP_DOM_DEFINE_LIST_EQUALITY_HELPER(xmlNs)
 
+static bool php_dom_is_equal_attr(const xmlAttr *this_attr, const xmlAttr *other_attr)
+{
+	ZEND_ASSERT(this_attr != NULL);
+	ZEND_ASSERT(other_attr != NULL);
+	return xmlStrEqual(this_attr->name, other_attr->name)
+		&& php_dom_node_is_ns_uri_equal((const xmlNode *) this_attr, (const xmlNode *) other_attr)
+		&& php_dom_node_is_content_equal((const xmlNode *) this_attr, (const xmlNode *) other_attr);
+}
+
 static bool php_dom_node_is_equal_node(const xmlNode *this, const xmlNode *other)
 {
 	ZEND_ASSERT(this != NULL);
@@ -1552,9 +1561,7 @@ static bool php_dom_node_is_equal_node(const xmlNode *this, const xmlNode *other
 	} else if (this->type == XML_ATTRIBUTE_NODE) {
 		const xmlAttr *this_attr = (const xmlAttr *) this;
 		const xmlAttr *other_attr = (const xmlAttr *) other;
-		return xmlStrEqual(this_attr->name, other_attr->name)
-			&& php_dom_node_is_ns_uri_equal(this, other)
-			&& php_dom_node_is_content_equal(this, other);
+		return php_dom_is_equal_attr(this_attr, other_attr);
 	} else if (this->type == XML_ENTITY_REF_NODE) {
 		return xmlStrEqual(this->name, other->name);
 	} else if (this->type == XML_ENTITY_DECL || this->type == XML_NOTATION_NODE || this->type == XML_ENTITY_NODE) {
@@ -2030,4 +2037,170 @@ PHP_METHOD(DOMNode, getRootNode)
 }
 /* }}} */
 
+/* {{{ URL: https://dom.spec.whatwg.org/#dom-node-comparedocumentposition (last check date 2023-07-24)
+Since:
+*/
+
+#define DOCUMENT_POSITION_DISCONNECTED 0x01
+#define DOCUMENT_POSITION_PRECEDING 0x02
+#define DOCUMENT_POSITION_FOLLOWING 0x04
+#define DOCUMENT_POSITION_CONTAINS 0x08
+#define DOCUMENT_POSITION_CONTAINED_BY 0x10
+#define DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC 0x20
+
+PHP_METHOD(DOMNode, compareDocumentPosition)
+{
+	zval *id, *node_zval;
+	xmlNodePtr other, this;
+	dom_object *this_intern, *other_intern;
+
+	if (zend_parse_parameters(ZEND_NUM_ARGS(), "O", &node_zval, dom_node_class_entry) == FAILURE) {
+		RETURN_THROWS();
+	}
+
+	DOM_GET_THIS_OBJ(this, id, xmlNodePtr, this_intern);
+	DOM_GET_OBJ(other, node_zval, xmlNodePtr, other_intern);
+
+	/* Step 1 */
+	if (this == other) {
+		RETURN_LONG(0);
+	}
+
+	/* Step 2 */
+	xmlNodePtr node1 = other;
+	xmlNodePtr node2 = this;
+
+	/* Step 3 */
+	xmlNodePtr attr1 = NULL;
+	xmlNodePtr attr2 = NULL;
+
+	/* Step 4 */
+	if (node1->type == XML_ATTRIBUTE_NODE) {
+		attr1 = node1;
+		node1 = attr1->parent;
+	}
+
+	/* Step 5 */
+	if (node2->type == XML_ATTRIBUTE_NODE) {
+		/* 5.1 */
+		attr2 = node2;
+		node2 = attr2->parent;
+
+		/* 5.2 */
+		if (attr1 != NULL && node1 != NULL && node2 == node1) {
+			for (const xmlAttr *attr = node2->properties; attr != NULL; attr = attr->next) {
+				if (php_dom_is_equal_attr(attr, (const xmlAttr *) attr1)) {
+					RETURN_LONG(DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC | DOCUMENT_POSITION_PRECEDING);
+				} else if (php_dom_is_equal_attr(attr, (const xmlAttr *) attr2)) {
+					RETURN_LONG(DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC | DOCUMENT_POSITION_FOLLOWING);
+				}
+			}
+		}
+	}
+
+	/* Step 6 */
+	/* We first check the first condition,
+	 * and as we need the root later anyway we'll cache the root and perform the root check after this if. */
+	if (node1 == NULL || node2 == NULL) {
+		goto disconnected;
+	}
+	bool node2_is_ancestor_of_node1 = false;
+	size_t node1_depth = 0;
+	xmlNodePtr node1_root = node1;
+	while (node1_root->parent) {
+		node1_root = node1_root->parent;
+		if (node1_root == node2) {
+			node2_is_ancestor_of_node1 = true;
+		}
+		node1_depth++;
+	}
+	bool node1_is_ancestor_of_node2 = false;
+	size_t node2_depth = 0;
+	xmlNodePtr node2_root = node2;
+	while (node2_root->parent) {
+		node2_root = node2_root->parent;
+		if (node2_root == node1) {
+			node1_is_ancestor_of_node2 = true;
+		}
+		node2_depth++;
+	}
+	/* Second condition from step 6 */
+	if (node1_root != node2_root) {
+		goto disconnected;
+	}
+
+	/* Step 7 */
+	if ((node1_is_ancestor_of_node2 && attr1 == NULL) || (node1 == node2 && attr2 != NULL)) {
+		RETURN_LONG(DOCUMENT_POSITION_CONTAINS | DOCUMENT_POSITION_PRECEDING);
+	}
+
+	/* Step 8 */
+	if ((node2_is_ancestor_of_node1 && attr2 == NULL) || (node1 == node2 && attr1 != NULL)) {
+		RETURN_LONG(DOCUMENT_POSITION_CONTAINED_BY | DOCUMENT_POSITION_FOLLOWING);
+	}
+
+	/* Special case: comparing children and attributes.
+	 * They belong to a different tree and are therefore hard to compare, but spec demands attributes to precede children
+	 * according to the pre-order depth-first search ordering.
+	 * Because their tree is different, the node parents only meet at the common element instead of earlier.
+	 * Therefore, it seems that one is the ancestor of the other. */
+	if (node1_is_ancestor_of_node2) {
+		ZEND_ASSERT(attr1 != NULL); /* Would've been handled in step 7 otherwise */
+		RETURN_LONG(DOCUMENT_POSITION_PRECEDING);
+	} else if (node2_is_ancestor_of_node1) {
+		ZEND_ASSERT(attr2 != NULL); /* Would've been handled in step 8 otherwise */
+		RETURN_LONG(DOCUMENT_POSITION_FOLLOWING);
+	}
+
+	/* Step 9 */
+
+	/* We'll use the following strategy (which was already prepared during step 6) to implement this efficiently:
+	 * 1. Move nodes upwards such that they are at the same depth.
+	 * 2. Then we move both nodes upwards simultaneously until their parents are equal.
+	 * 3. If we then move node1 to the next entry repeatedly and we encounter node2,
+	 *    then we know node1 precedes node2. Otherwise, node2 must precede node1. */
+	/* 1. */
+	if (node1_depth > node2_depth) {
+		do {
+			node1 = node1->parent;
+			node1_depth--;
+		} while (node1_depth > node2_depth);
+	} else if (node2_depth > node1_depth) {
+		do {
+			node2 = node2->parent;
+			node2_depth--;
+		} while (node2_depth > node1_depth);
+	}
+	/* 2. */
+	while (node1->parent != node2->parent) {
+		node1 = node1->parent;
+		node2 = node2->parent;
+	}
+	/* 3. */
+	ZEND_ASSERT(node1 != node2);
+	ZEND_ASSERT(node1 != NULL);
+	ZEND_ASSERT(node2 != NULL);
+	do {
+		node1 = node1->next;
+		if (node1 == node2) {
+			RETURN_LONG(DOCUMENT_POSITION_PRECEDING);
+		}
+	} while (node1 != NULL);
+
+	/* Step 10 */
+	RETURN_LONG(DOCUMENT_POSITION_FOLLOWING);
+
+disconnected:;
+	zend_long ordering;
+	if (UNEXPECTED(node1 == node2)) {
+		/* Degenerate case, they're both NULL, but the ordering must be consistent... */
+		ZEND_ASSERT(node1 == NULL);
+		ordering = other_intern < this_intern ? DOCUMENT_POSITION_PRECEDING : DOCUMENT_POSITION_FOLLOWING;
+	} else {
+		ordering = node1 < node2 ? DOCUMENT_POSITION_PRECEDING : DOCUMENT_POSITION_FOLLOWING;
+	}
+	RETURN_LONG(DOCUMENT_POSITION_DISCONNECTED | DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC | ordering);
+}
+/* }}} */
+
 #endif
diff --git a/ext/dom/php_dom.stub.php b/ext/dom/php_dom.stub.php
index 7316f8426698b..bc1033b29df74 100644
--- a/ext/dom/php_dom.stub.php
+++ b/ext/dom/php_dom.stub.php
@@ -297,6 +297,13 @@ public function replaceWith(...$nodes): void;
 /** @not-serializable */
 class DOMNode
 {
+    public const int DOCUMENT_POSITION_DISCONNECTED = 0x01;
+    public const int DOCUMENT_POSITION_PRECEDING = 0x02;
+    public const int DOCUMENT_POSITION_FOLLOWING = 0x04;
+    public const int DOCUMENT_POSITION_CONTAINS = 0x08;
+    public const int DOCUMENT_POSITION_CONTAINED_BY = 0x10;
+    public const int DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC = 0x20;
+
     /** @readonly */
     public string $nodeName;
 
@@ -404,6 +411,8 @@ public function replaceChild(DOMNode $node, DOMNode $child) {}
     public function contains(DOMNode|DOMNameSpaceNode|null $other): bool {}
 
     public function getRootNode(?array $options = null): DOMNode {}
+
+    public function compareDocumentPosition(DOMNode $other): int {}
 }
 
 /** @not-serializable */
diff --git a/ext/dom/php_dom_arginfo.h b/ext/dom/php_dom_arginfo.h
index 76d8b0af2b0b5..1b7fc063fa2d6 100644
--- a/ext/dom/php_dom_arginfo.h
+++ b/ext/dom/php_dom_arginfo.h
@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: ebe9bcbd185e1973b5447beb306bd9d93051f415 */
+ * Stub hash: 4705229124ee243538e712f4af1d94ddc4c3be0b */
 
 ZEND_BEGIN_ARG_WITH_RETURN_OBJ_INFO_EX(arginfo_dom_import_simplexml, 0, 1, DOMElement, 0)
 	ZEND_ARG_TYPE_INFO(0, node, IS_OBJECT, 0)
@@ -114,6 +114,10 @@ ZEND_BEGIN_ARG_WITH_RETURN_OBJ_INFO_EX(arginfo_class_DOMNode_getRootNode, 0, 0,
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, options, IS_ARRAY, 1, "null")
 ZEND_END_ARG_INFO()
 
+ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_class_DOMNode_compareDocumentPosition, 0, 1, IS_LONG, 0)
+	ZEND_ARG_OBJ_INFO(0, other, DOMNode, 0)
+ZEND_END_ARG_INFO()
+
 ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_DOMImplementation_getFeature, 0, 2, IS_NEVER, 0)
 	ZEND_ARG_TYPE_INFO(0, feature, IS_STRING, 0)
 	ZEND_ARG_TYPE_INFO(0, version, IS_STRING, 0)
@@ -553,6 +557,7 @@ ZEND_METHOD(DOMNode, removeChild);
 ZEND_METHOD(DOMNode, replaceChild);
 ZEND_METHOD(DOMNode, contains);
 ZEND_METHOD(DOMNode, getRootNode);
+ZEND_METHOD(DOMNode, compareDocumentPosition);
 ZEND_METHOD(DOMImplementation, getFeature);
 ZEND_METHOD(DOMImplementation, hasFeature);
 ZEND_METHOD(DOMImplementation, createDocumentType);
@@ -745,6 +750,7 @@ static const zend_function_entry class_DOMNode_methods[] = {
 	ZEND_ME(DOMNode, replaceChild, arginfo_class_DOMNode_replaceChild, ZEND_ACC_PUBLIC)
 	ZEND_ME(DOMNode, contains, arginfo_class_DOMNode_contains, ZEND_ACC_PUBLIC)
 	ZEND_ME(DOMNode, getRootNode, arginfo_class_DOMNode_getRootNode, ZEND_ACC_PUBLIC)
+	ZEND_ME(DOMNode, compareDocumentPosition, arginfo_class_DOMNode_compareDocumentPosition, ZEND_ACC_PUBLIC)
 	ZEND_FE_END
 };
 
@@ -1098,6 +1104,42 @@ static zend_class_entry *register_class_DOMNode(void)
 	class_entry = zend_register_internal_class_ex(&ce, NULL);
 	class_entry->ce_flags |= ZEND_ACC_NOT_SERIALIZABLE;
 
+	zval const_DOCUMENT_POSITION_DISCONNECTED_value;
+	ZVAL_LONG(&const_DOCUMENT_POSITION_DISCONNECTED_value, 0x1);
+	zend_string *const_DOCUMENT_POSITION_DISCONNECTED_name = zend_string_init_interned("DOCUMENT_POSITION_DISCONNECTED", sizeof("DOCUMENT_POSITION_DISCONNECTED") - 1, 1);
+	zend_declare_typed_class_constant(class_entry, const_DOCUMENT_POSITION_DISCONNECTED_name, &const_DOCUMENT_POSITION_DISCONNECTED_value, ZEND_ACC_PUBLIC, NULL, (zend_type) ZEND_TYPE_INIT_MASK(MAY_BE_LONG));
+	zend_string_release(const_DOCUMENT_POSITION_DISCONNECTED_name);
+
+	zval const_DOCUMENT_POSITION_PRECEDING_value;
+	ZVAL_LONG(&const_DOCUMENT_POSITION_PRECEDING_value, 0x2);
+	zend_string *const_DOCUMENT_POSITION_PRECEDING_name = zend_string_init_interned("DOCUMENT_POSITION_PRECEDING", sizeof("DOCUMENT_POSITION_PRECEDING") - 1, 1);
+	zend_declare_typed_class_constant(class_entry, const_DOCUMENT_POSITION_PRECEDING_name, &const_DOCUMENT_POSITION_PRECEDING_value, ZEND_ACC_PUBLIC, NULL, (zend_type) ZEND_TYPE_INIT_MASK(MAY_BE_LONG));
+	zend_string_release(const_DOCUMENT_POSITION_PRECEDING_name);
+
+	zval const_DOCUMENT_POSITION_FOLLOWING_value;
+	ZVAL_LONG(&const_DOCUMENT_POSITION_FOLLOWING_value, 0x4);
+	zend_string *const_DOCUMENT_POSITION_FOLLOWING_name = zend_string_init_interned("DOCUMENT_POSITION_FOLLOWING", sizeof("DOCUMENT_POSITION_FOLLOWING") - 1, 1);
+	zend_declare_typed_class_constant(class_entry, const_DOCUMENT_POSITION_FOLLOWING_name, &const_DOCUMENT_POSITION_FOLLOWING_value, ZEND_ACC_PUBLIC, NULL, (zend_type) ZEND_TYPE_INIT_MASK(MAY_BE_LONG));
+	zend_string_release(const_DOCUMENT_POSITION_FOLLOWING_name);
+
+	zval const_DOCUMENT_POSITION_CONTAINS_value;
+	ZVAL_LONG(&const_DOCUMENT_POSITION_CONTAINS_value, 0x8);
+	zend_string *const_DOCUMENT_POSITION_CONTAINS_name = zend_string_init_interned("DOCUMENT_POSITION_CONTAINS", sizeof("DOCUMENT_POSITION_CONTAINS") - 1, 1);
+	zend_declare_typed_class_constant(class_entry, const_DOCUMENT_POSITION_CONTAINS_name, &const_DOCUMENT_POSITION_CONTAINS_value, ZEND_ACC_PUBLIC, NULL, (zend_type) ZEND_TYPE_INIT_MASK(MAY_BE_LONG));
+	zend_string_release(const_DOCUMENT_POSITION_CONTAINS_name);
+
+	zval const_DOCUMENT_POSITION_CONTAINED_BY_value;
+	ZVAL_LONG(&const_DOCUMENT_POSITION_CONTAINED_BY_value, 0x10);
+	zend_string *const_DOCUMENT_POSITION_CONTAINED_BY_name = zend_string_init_interned("DOCUMENT_POSITION_CONTAINED_BY", sizeof("DOCUMENT_POSITION_CONTAINED_BY") - 1, 1);
+	zend_declare_typed_class_constant(class_entry, const_DOCUMENT_POSITION_CONTAINED_BY_name, &const_DOCUMENT_POSITION_CONTAINED_BY_value, ZEND_ACC_PUBLIC, NULL, (zend_type) ZEND_TYPE_INIT_MASK(MAY_BE_LONG));
+	zend_string_release(const_DOCUMENT_POSITION_CONTAINED_BY_name);
+
+	zval const_DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC_value;
+	ZVAL_LONG(&const_DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC_value, 0x20);
+	zend_string *const_DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC_name = zend_string_init_interned("DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC", sizeof("DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC") - 1, 1);
+	zend_declare_typed_class_constant(class_entry, const_DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC_name, &const_DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC_value, ZEND_ACC_PUBLIC, NULL, (zend_type) ZEND_TYPE_INIT_MASK(MAY_BE_LONG));
+	zend_string_release(const_DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC_name);
+
 	zval property_nodeName_default_value;
 	ZVAL_UNDEF(&property_nodeName_default_value);
 	zend_string *property_nodeName_name = zend_string_init("nodeName", sizeof("nodeName") - 1, 1);
diff --git a/ext/dom/tests/compareDocumentPosition/attribute_child_order.phpt b/ext/dom/tests/compareDocumentPosition/attribute_child_order.phpt
new file mode 100644
index 0000000000000..84137dcbaa347
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/attribute_child_order.phpt
@@ -0,0 +1,53 @@
+--TEST--
+compareDocumentPosition: attribute vs child order
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<container>
+<before/>
+<outer align="center">
+    <p>foo</p>
+    <div>
+        <div>
+            <p>bar</p>
+        </div>
+    </div>
+</outer>
+</container>
+XML);
+
+$before = $dom->documentElement->firstElementChild;
+$outer = $before->nextElementSibling;
+$foo = $outer->firstElementChild;
+$bar = $foo->nextElementSibling->firstElementChild->firstElementChild;
+
+// See note about attributes vs children positions: attributes precede children
+
+echo "--- outer attribute vs before ---\n";
+var_dump($outer->attributes[0]->compareDocumentPosition($before) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+var_dump($before->compareDocumentPosition($outer->attributes[0]) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+
+echo "--- outer attribute vs foo ---\n";
+var_dump($outer->attributes[0]->compareDocumentPosition($foo) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+var_dump($foo->compareDocumentPosition($outer->attributes[0]) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+
+echo "--- outer attribute vs bar ---\n";
+var_dump($outer->attributes[0]->compareDocumentPosition($bar) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+var_dump($bar->compareDocumentPosition($outer->attributes[0]) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+
+?>
+--EXPECT--
+--- outer attribute vs before ---
+bool(true)
+bool(true)
+--- outer attribute vs foo ---
+bool(true)
+bool(true)
+--- outer attribute vs bar ---
+bool(true)
+bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/attribute_order_different_element.phpt b/ext/dom/tests/compareDocumentPosition/attribute_order_different_element.phpt
new file mode 100644
index 0000000000000..fed5f9c316b62
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/attribute_order_different_element.phpt
@@ -0,0 +1,54 @@
+--TEST--
+compareDocumentPosition: attribute order for different element
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<outer>
+    <inner a="b" c="d" e="f" />
+    <inner a="b" x="y" />
+</outer>
+XML);
+
+$attrs1 = $dom->documentElement->firstElementChild->attributes;
+$attrs2 = $dom->documentElement->firstElementChild->nextElementSibling->attributes;
+
+foreach ($attrs1 as $attr1) {
+    foreach ($attrs2 as $attr2) {
+        echo "--- Compare 1->2 {$attr1->name} and {$attr2->name} ---\n";
+        var_dump($attr1->compareDocumentPosition($attr2) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+        echo "--- Compare 2->1 {$attr1->name} and {$attr2->name} ---\n";
+        var_dump($attr2->compareDocumentPosition($attr1) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+    }
+}
+
+?>
+--EXPECT--
+--- Compare 1->2 a and a ---
+bool(true)
+--- Compare 2->1 a and a ---
+bool(true)
+--- Compare 1->2 a and x ---
+bool(true)
+--- Compare 2->1 a and x ---
+bool(true)
+--- Compare 1->2 c and a ---
+bool(true)
+--- Compare 2->1 c and a ---
+bool(true)
+--- Compare 1->2 c and x ---
+bool(true)
+--- Compare 2->1 c and x ---
+bool(true)
+--- Compare 1->2 e and a ---
+bool(true)
+--- Compare 2->1 e and a ---
+bool(true)
+--- Compare 1->2 e and x ---
+bool(true)
+--- Compare 2->1 e and x ---
+bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/attribute_order_same_element.phpt b/ext/dom/tests/compareDocumentPosition/attribute_order_same_element.phpt
new file mode 100644
index 0000000000000..1987d179ea0e8
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/attribute_order_same_element.phpt
@@ -0,0 +1,40 @@
+--TEST--
+compareDocumentPosition: attribute order for same element
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<container a="b" c="d" e="f" />
+XML);
+
+$attrs = $dom->documentElement->attributes;
+for ($i = 0; $i <= 2; $i++) {
+    for ($j = $i + 1; $j <= $i + 2; $j++) {
+        echo "--- Compare $i and ", ($j % 3), " ---\n";
+        if ($i < ($j % 3)) {
+            $expected = DOMNode::DOCUMENT_POSITION_FOLLOWING | DOMNode::DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC;
+        } else {
+            $expected = DOMNode::DOCUMENT_POSITION_PRECEDING | DOMNode::DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC;
+        }
+        var_dump($attrs[$i]->compareDocumentPosition($attrs[$j % 3]) === $expected);
+    }
+}
+
+?>
+--EXPECT--
+--- Compare 0 and 1 ---
+bool(true)
+--- Compare 0 and 2 ---
+bool(true)
+--- Compare 1 and 2 ---
+bool(true)
+--- Compare 1 and 0 ---
+bool(true)
+--- Compare 2 and 0 ---
+bool(true)
+--- Compare 2 and 1 ---
+bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/contains_attribute_direct_descendent.phpt b/ext/dom/tests/compareDocumentPosition/contains_attribute_direct_descendent.phpt
new file mode 100644
index 0000000000000..0cf5785988bb9
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/contains_attribute_direct_descendent.phpt
@@ -0,0 +1,23 @@
+--TEST--
+compareDocumentPosition: contains attribute as a direct descendent
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<container align="center"/>
+XML);
+
+$container = $dom->documentElement;
+$attribute = $container->attributes[0];
+
+var_dump($container->compareDocumentPosition($attribute) === (DOMNode::DOCUMENT_POSITION_FOLLOWING | DOMNode::DOCUMENT_POSITION_CONTAINED_BY));
+var_dump($attribute->compareDocumentPosition($container) === (DOMNode::DOCUMENT_POSITION_PRECEDING | DOMNode::DOCUMENT_POSITION_CONTAINS));
+
+?>
+--EXPECT--
+bool(true)
+bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/contains_attribute_freestanding.phpt b/ext/dom/tests/compareDocumentPosition/contains_attribute_freestanding.phpt
new file mode 100644
index 0000000000000..d13208cddda03
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/contains_attribute_freestanding.phpt
@@ -0,0 +1,22 @@
+--TEST--
+compareDocumentPosition: contains attribute for a freestanding element
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$foo = $dom->createElement("foo");
+$foo->setAttribute("test", "value");
+$attribute = $foo->attributes[0];
+
+echo $dom->saveXML($foo), "\n";
+
+var_dump($foo->compareDocumentPosition($attribute) === (DOMNode::DOCUMENT_POSITION_FOLLOWING | DOMNode::DOCUMENT_POSITION_CONTAINED_BY));
+var_dump($attribute->compareDocumentPosition($foo) === (DOMNode::DOCUMENT_POSITION_PRECEDING | DOMNode::DOCUMENT_POSITION_CONTAINS));
+
+?>
+--EXPECT--
+<foo test="value"/>
+bool(true)
+bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/contains_attribute_longer_descendent.phpt b/ext/dom/tests/compareDocumentPosition/contains_attribute_longer_descendent.phpt
new file mode 100644
index 0000000000000..f95a35edc78f7
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/contains_attribute_longer_descendent.phpt
@@ -0,0 +1,28 @@
+--TEST--
+compareDocumentPosition: contains attribute as a descendent in a longer path
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<container>
+    <div>
+        <p align="center"/>
+    </div>
+</container>
+XML);
+
+$container = $dom->documentElement;
+$p = $container->firstElementChild->firstElementChild;
+$attribute = $p->attributes[0];
+
+var_dump($container->compareDocumentPosition($attribute) === (DOMNode::DOCUMENT_POSITION_FOLLOWING | DOMNode::DOCUMENT_POSITION_CONTAINED_BY));
+var_dump($attribute->compareDocumentPosition($container) === (DOMNode::DOCUMENT_POSITION_PRECEDING | DOMNode::DOCUMENT_POSITION_CONTAINS));
+
+?>
+--EXPECT--
+bool(true)
+bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/contains_element_direct_descendent.phpt b/ext/dom/tests/compareDocumentPosition/contains_element_direct_descendent.phpt
new file mode 100644
index 0000000000000..5e00c8ec49719
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/contains_element_direct_descendent.phpt
@@ -0,0 +1,25 @@
+--TEST--
+compareDocumentPosition: contains nodes as a direct descendent
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<container>
+<div/>
+</container>
+XML);
+
+$container = $dom->documentElement;
+$div = $container->firstChild;
+
+var_dump($container->compareDocumentPosition($div) === (DOMNode::DOCUMENT_POSITION_FOLLOWING | DOMNode::DOCUMENT_POSITION_CONTAINED_BY));
+var_dump($div->compareDocumentPosition($container) === (DOMNode::DOCUMENT_POSITION_PRECEDING | DOMNode::DOCUMENT_POSITION_CONTAINS));
+
+?>
+--EXPECT--
+bool(true)
+bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/contains_element_longer_descendent.phpt b/ext/dom/tests/compareDocumentPosition/contains_element_longer_descendent.phpt
new file mode 100644
index 0000000000000..8557b5407e0f4
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/contains_element_longer_descendent.phpt
@@ -0,0 +1,44 @@
+--TEST--
+compareDocumentPosition: contains nodes as a descendent in a longer path
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<container>
+    <a>
+        <b/>
+        <c>
+            <d/>
+        </c>
+    </a>
+</container>
+XML);
+
+$xpath = new DOMXPath($dom);
+$container = $xpath->query("//container")->item(0);
+
+foreach (["a", "b", "c", "d"] as $tag) {
+    echo "--- Test $tag ---\n";
+    $element = $xpath->query("//$tag")->item(0);
+    var_dump($container->compareDocumentPosition($element) === (DOMNode::DOCUMENT_POSITION_FOLLOWING | DOMNode::DOCUMENT_POSITION_CONTAINED_BY));
+    var_dump($element->compareDocumentPosition($container) === (DOMNode::DOCUMENT_POSITION_PRECEDING | DOMNode::DOCUMENT_POSITION_CONTAINS));    
+}
+
+?>
+--EXPECT--
+--- Test a ---
+bool(true)
+bool(true)
+--- Test b ---
+bool(true)
+bool(true)
+--- Test c ---
+bool(true)
+bool(true)
+--- Test d ---
+bool(true)
+bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/disconnected.phpt b/ext/dom/tests/compareDocumentPosition/disconnected.phpt
new file mode 100644
index 0000000000000..75b262b9848e1
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/disconnected.phpt
@@ -0,0 +1,68 @@
+--TEST--
+compareDocumentPosition: disconnected
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+function check($element1, $element2) {
+    echo "Disconnect and implementation flag (1->2): ";
+    var_dump(($element1->compareDocumentPosition($element2) & (DOMNode::DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC | DOMNode::DOCUMENT_POSITION_DISCONNECTED)) === (DOMNode::DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC | DOMNode::DOCUMENT_POSITION_DISCONNECTED));
+    echo "Disconnect and implementation flag (2->1): ";
+    var_dump(($element2->compareDocumentPosition($element1) & (DOMNode::DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC | DOMNode::DOCUMENT_POSITION_DISCONNECTED)) === (DOMNode::DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC | DOMNode::DOCUMENT_POSITION_DISCONNECTED));
+    
+    // Must be the opposite result
+    echo "Opposite result: ";
+    if ($element1->compareDocumentPosition($element2) & DOMNode::DOCUMENT_POSITION_FOLLOWING) {
+        var_dump(($element2->compareDocumentPosition($element1) & DOMNode::DOCUMENT_POSITION_PRECEDING) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+    } else {
+        var_dump(($element2->compareDocumentPosition($element1) & DOMNode::DOCUMENT_POSITION_FOLLOWING) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+    }
+}
+
+$dom1 = new DOMDocument();
+$dom1->loadXML('<?xml version="1.0"?><container/>');
+$dom2 = new DOMDocument();
+$dom2->loadXML('<?xml version="1.0"?><container/>');
+
+echo "--- Two documents ---\n";
+check($dom1, $dom2);
+echo "--- Two document roots ---\n";
+check($dom1->documentElement, $dom2->documentElement);
+echo "--- Fragment ---\n";
+$fragment = $dom1->createDocumentFragment();
+$foo = $fragment->appendChild(new DOMText("foo"));
+check($foo, $dom1);
+echo "--- Unattached element ---\n";
+check(new DOMElement("foo"), new DOMElement("bar"));
+echo "--- Unattached attribute ---\n";
+check(new DOMAttr("foo"), new DOMAttr("bar"));
+echo "--- Unattached attribute & element ---\n";
+check(new DOMAttr("foo"), new DOMElement("bar"));
+
+?>
+--EXPECT--
+--- Two documents ---
+Disconnect and implementation flag (1->2): bool(true)
+Disconnect and implementation flag (2->1): bool(true)
+Opposite result: bool(true)
+--- Two document roots ---
+Disconnect and implementation flag (1->2): bool(true)
+Disconnect and implementation flag (2->1): bool(true)
+Opposite result: bool(true)
+--- Fragment ---
+Disconnect and implementation flag (1->2): bool(true)
+Disconnect and implementation flag (2->1): bool(true)
+Opposite result: bool(true)
+--- Unattached element ---
+Disconnect and implementation flag (1->2): bool(true)
+Disconnect and implementation flag (2->1): bool(true)
+Opposite result: bool(true)
+--- Unattached attribute ---
+Disconnect and implementation flag (1->2): bool(true)
+Disconnect and implementation flag (2->1): bool(true)
+Opposite result: bool(true)
+--- Unattached attribute & element ---
+Disconnect and implementation flag (1->2): bool(true)
+Disconnect and implementation flag (2->1): bool(true)
+Opposite result: bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/element_order_different_depth.phpt b/ext/dom/tests/compareDocumentPosition/element_order_different_depth.phpt
new file mode 100644
index 0000000000000..cca1174961db9
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/element_order_different_depth.phpt
@@ -0,0 +1,50 @@
+--TEST--
+compareDocumentPosition: element order at a different tree depth
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<container>
+    <div>
+        <p>foo</p>
+    </div>
+    <div>
+        <div>
+            <p>bar</p>
+        </div>
+    </div>
+</container>
+XML);
+
+$xpath = new DOMXPath($dom);
+$query = $xpath->query("//p");
+$foo = $query->item(0);
+$bar = $query->item(1);
+
+for ($i = 0; $i < 2; $i++) {
+    echo "--- Check on depth $i ---\n";
+    var_dump($foo->compareDocumentPosition($bar) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+    var_dump($bar->compareDocumentPosition($foo) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+    $foo = $foo->parentElement;
+    $bar = $bar->parentElement;
+}
+
+echo "--- One contains the other at depth 2 ---\n";
+var_dump(boolval($foo->compareDocumentPosition($bar) & DOMNode::DOCUMENT_POSITION_CONTAINED_BY));
+var_dump(boolval($bar->compareDocumentPosition($foo) & DOMNode::DOCUMENT_POSITION_CONTAINS));
+
+?>
+--EXPECT--
+--- Check on depth 0 ---
+bool(true)
+bool(true)
+--- Check on depth 1 ---
+bool(true)
+bool(true)
+--- One contains the other at depth 2 ---
+bool(true)
+bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/element_order_direct_root_children.phpt b/ext/dom/tests/compareDocumentPosition/element_order_direct_root_children.phpt
new file mode 100644
index 0000000000000..b45f2435d7090
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/element_order_direct_root_children.phpt
@@ -0,0 +1,18 @@
+--TEST--
+compareDocumentPosition: direct root children
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$foo = $dom->appendChild($dom->createElement("foo"));
+$bar = $dom->appendChild($dom->createElement("bar"));
+
+var_dump($foo->compareDocumentPosition($bar) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+var_dump($bar->compareDocumentPosition($foo) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+
+?>
+--EXPECT--
+bool(true)
+bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/element_order_same_depth.phpt b/ext/dom/tests/compareDocumentPosition/element_order_same_depth.phpt
new file mode 100644
index 0000000000000..e079b1c8d5566
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/element_order_same_depth.phpt
@@ -0,0 +1,71 @@
+--TEST--
+compareDocumentPosition: element order at the same tree depth
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<container>
+    <div>
+        <div>
+            <strong/>
+            <p>foo</p>
+        </div>
+    </div>
+    <div>
+        <div>
+            <p>bar</p>
+            <strong/>
+        </div>
+    </div>
+</container>
+XML);
+
+$xpath = new DOMXPath($dom);
+$query = $xpath->query("//p");
+$foo = $query->item(0);
+$bar = $query->item(1);
+
+echo "--- strong & foo ---\n";
+var_dump($foo->previousElementSibling->compareDocumentPosition($foo) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+var_dump($foo->compareDocumentPosition($foo->previousElementSibling) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+
+echo "--- strong & bar ---\n";
+var_dump($bar->nextElementSibling->compareDocumentPosition($bar) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+var_dump($bar->compareDocumentPosition($bar->nextElementSibling) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+
+echo "--- strong & strong ---\n";
+var_dump($foo->previousElementSibling->compareDocumentPosition($bar->nextElementSibling) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+var_dump($bar->nextElementSibling->compareDocumentPosition($foo->previousElementSibling) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+
+for ($i = 0; $i < 3; $i++) {
+    echo "--- Check on depth $i ---\n";
+    var_dump($foo->compareDocumentPosition($bar) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+    var_dump($bar->compareDocumentPosition($foo) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+    $foo = $foo->parentElement;
+    $bar = $bar->parentElement;
+}
+
+?>
+--EXPECT--
+--- strong & foo ---
+bool(true)
+bool(true)
+--- strong & bar ---
+bool(true)
+bool(true)
+--- strong & strong ---
+bool(true)
+bool(true)
+--- Check on depth 0 ---
+bool(true)
+bool(true)
+--- Check on depth 1 ---
+bool(true)
+bool(true)
+--- Check on depth 2 ---
+bool(true)
+bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/entity.phpt b/ext/dom/tests/compareDocumentPosition/entity.phpt
new file mode 100644
index 0000000000000..318053c454f9b
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/entity.phpt
@@ -0,0 +1,51 @@
+--TEST--
+compareDocumentPosition: entity ordering
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<!DOCTYPE root [
+<!ENTITY e1 "e1">
+<!ENTITY e2 "e2">
+]>
+<container>
+    <child>&e1;</child>
+</container>
+XML, LIBXML_NOENT);
+
+$entities = iterator_to_array($dom->doctype->entities);
+usort($entities, fn ($a, $b) => strcmp($a->nodeName, $b->nodeName));
+
+echo "--- Compare entities ---\n";
+
+var_dump($entities[0]->compareDocumentPosition($entities[1]) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+var_dump($entities[1]->compareDocumentPosition($entities[0]) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+
+$xpath = new DOMXPath($dom);
+$child = $xpath->query('//child')->item(0);
+
+echo "--- Compare entities against first child ---\n";
+
+var_dump($entities[0]->compareDocumentPosition($child->firstChild) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+var_dump($entities[1]->compareDocumentPosition($child->firstChild) === DOMNode::DOCUMENT_POSITION_FOLLOWING);
+
+echo "--- Compare first child against entities ---\n";
+
+var_dump($child->firstChild->compareDocumentPosition($entities[0]) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+var_dump($child->firstChild->compareDocumentPosition($entities[1]) === DOMNode::DOCUMENT_POSITION_PRECEDING);
+
+?>
+--EXPECT--
+--- Compare entities ---
+bool(true)
+bool(true)
+--- Compare entities against first child ---
+bool(true)
+bool(true)
+--- Compare first child against entities ---
+bool(true)
+bool(true)
diff --git a/ext/dom/tests/compareDocumentPosition/equal.phpt b/ext/dom/tests/compareDocumentPosition/equal.phpt
new file mode 100644
index 0000000000000..31f30d542b406
--- /dev/null
+++ b/ext/dom/tests/compareDocumentPosition/equal.phpt
@@ -0,0 +1,29 @@
+--TEST--
+compareDocumentPosition: equal nodes
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = new DOMDocument();
+$dom->loadXML(<<<XML
+<?xml version="1.0"?>
+<container>
+<p>foo</p>
+<p>foo</p>
+</container>
+XML);
+
+$xpath = new DOMXPath($dom);
+$nodes = $xpath->query('//p');
+var_dump($nodes->item(0)->compareDocumentPosition($nodes->item(0)) === 0);
+var_dump($nodes->item(1)->compareDocumentPosition($nodes->item(1)) === 0);
+var_dump($nodes->item(0)->compareDocumentPosition($nodes->item(1)) === 0);
+var_dump($nodes->item(1)->compareDocumentPosition($nodes->item(0)) === 0);
+
+?>
+--EXPECT--
+bool(true)
+bool(true)
+bool(false)
+bool(false)