diff --git a/ext/dom/parentnode.c b/ext/dom/parentnode.c
index cf823057d22ae..46c90a13e31d5 100644
--- a/ext/dom/parentnode.c
+++ b/ext/dom/parentnode.c
@@ -124,6 +124,23 @@ int dom_parent_node_child_element_count(dom_object *obj, zval *retval)
 }
 /* }}} */
 
+static bool dom_is_node_in_list(const zval *nodes, int nodesc, const xmlNodePtr node_to_find)
+{
+	for (int i = 0; i < nodesc; i++) {
+		if (Z_TYPE(nodes[i]) == IS_OBJECT) {
+			const zend_class_entry *ce = Z_OBJCE(nodes[i]);
+
+			if (instanceof_function(ce, dom_node_class_entry)) {
+				if (dom_object_get_node(Z_DOMOBJ_P(nodes + i)) == node_to_find) {
+					return true;
+				}
+			}
+		}
+	}
+
+	return false;
+}
+
 xmlNode* dom_zvals_to_fragment(php_libxml_ref_obj *document, xmlNode *contextNode, zval *nodes, int nodesc)
 {
 	int i;
@@ -177,17 +194,16 @@ xmlNode* dom_zvals_to_fragment(php_libxml_ref_obj *document, xmlNode *contextNod
 					goto hierarchy_request_err;
 				}
 
-				/*
-				 * xmlNewDocText function will always returns same address to the second parameter if the parameters are greater than or equal to three.
-				 * If it's text, that's fine, but if it's an object, it can cause invalid pointer because many new nodes point to the same memory address.
-				 * So we must copy the new node to avoid this situation.
-				 */
-				if (nodesc > 1) {
+				/* Citing from the docs (https://gnome.pages.gitlab.gnome.org/libxml2/devhelp/libxml2-tree.html#xmlAddChild): 
+				 * "Add a new node to @parent, at the end of the child (or property) list merging adjacent TEXT nodes (in which case @cur is freed)".
+				 * So we must take a copy if this situation arises to prevent a use-after-free. */
+				bool will_free = newNode->type == XML_TEXT_NODE && fragment->last && fragment->last->type == XML_TEXT_NODE;
+				if (will_free) {
 					newNode = xmlCopyNode(newNode, 1);
 				}
 
 				if (!xmlAddChild(fragment, newNode)) {
-					if (nodesc > 1) {
+					if (will_free) {
 						xmlFreeNode(newNode);
 					}
 					goto hierarchy_request_err;
@@ -303,25 +319,64 @@ void dom_parent_node_prepend(dom_object *context, zval *nodes, int nodesc)
 	xmlFree(fragment);
 }
 
+static void dom_pre_insert(xmlNodePtr insertion_point, xmlNodePtr parentNode, xmlNodePtr newchild, xmlNodePtr fragment)
+{
+	if (!insertion_point) {
+		/* Place it as last node */
+		if (parentNode->children) {
+			/* There are children */
+			fragment->last->prev = parentNode->last;
+			newchild->prev = parentNode->last->prev;
+			parentNode->last->next = newchild;
+		} else {
+			/* No children, because they moved out when they became a fragment */
+			parentNode->children = newchild;
+			parentNode->last = newchild;
+		}
+	} else {
+		/* Insert fragment before insertion_point */
+		fragment->last->next = insertion_point;
+		if (insertion_point->prev) {
+			insertion_point->prev->next = newchild;
+			newchild->prev = insertion_point->prev;
+		}
+		insertion_point->prev = newchild;
+		if (parentNode->children == insertion_point) {
+			parentNode->children = newchild;
+		}
+	}
+}
+
 void dom_parent_node_after(dom_object *context, zval *nodes, int nodesc)
 {
+	/* Spec link: https://dom.spec.whatwg.org/#dom-childnode-after */
+
 	xmlNode *prevsib = dom_object_get_node(context);
 	xmlNodePtr newchild, parentNode;
-	xmlNode *fragment, *nextsib;
+	xmlNode *fragment;
 	xmlDoc *doc;
-	bool afterlastchild;
-
-	int stricterror = dom_get_strict_error(context->document);
 
-	if (!prevsib->parent) {
-		php_dom_throw_error(NO_MODIFICATION_ALLOWED_ERR, stricterror);
+	/* Spec step 1 */
+	parentNode = prevsib->parent;
+	/* Spec step 2 */
+	if (!parentNode) {
+		int stricterror = dom_get_strict_error(context->document);
+		php_dom_throw_error(HIERARCHY_REQUEST_ERR, stricterror);
 		return;
 	}
 
+	/* Spec step 3: find first following child not in nodes; otherwise null */
+	xmlNodePtr viable_next_sibling = prevsib->next;
+	while (viable_next_sibling) {
+		if (!dom_is_node_in_list(nodes, nodesc, viable_next_sibling)) {
+			break;
+		}
+		viable_next_sibling = viable_next_sibling->next;
+	}
+
 	doc = prevsib->doc;
-	parentNode = prevsib->parent;
-	nextsib = prevsib->next;
-	afterlastchild = (nextsib == NULL);
+
+	/* Spec step 4: convert nodes into fragment */
 	fragment = dom_zvals_to_fragment(context->document, parentNode, nodes, nodesc);
 
 	if (fragment == NULL) {
@@ -331,40 +386,9 @@ void dom_parent_node_after(dom_object *context, zval *nodes, int nodesc)
 	newchild = fragment->children;
 
 	if (newchild) {
-		/* first node and last node are both both parameters to DOMElement::after() method so nextsib and prevsib are null. */
-		if (!parentNode->children) {
-			prevsib = nextsib = NULL;
-		} else if (afterlastchild) {
-			/*
-			 * The new node will be inserted after last node, prevsib is last node.
-			 * The first node is the parameter to DOMElement::after() if parentNode->children == prevsib is true
-			 * and prevsib does not change, otherwise prevsib is parentNode->last (first node).
-			 */
-			prevsib = parentNode->children == prevsib ? prevsib : parentNode->last;
-		} else {
-			/*
-			 * The new node will be inserted after first node, prevsib is first node.
-			 * The first node is not the parameter to DOMElement::after() if parentNode->children == prevsib is true
-			 * and prevsib does not change otherwise prevsib is null to mean that parentNode->children is the new node.
-			 */
-			prevsib = parentNode->children == prevsib ? prevsib : NULL;
-		}
-
-		if (prevsib) {
-			fragment->last->next = prevsib->next;
-			if (prevsib->next) {
-				prevsib->next->prev = fragment->last;
-			}
-			prevsib->next = newchild;
-		} else {
-			parentNode->children = newchild;
-			if (nextsib) {
-				fragment->last->next = nextsib;
-				nextsib->prev = fragment->last;
-			}
-		}
+		/* Step 5: place fragment into the parent before viable_next_sibling */
+		dom_pre_insert(viable_next_sibling, parentNode, newchild, fragment);
 
-		newchild->prev = prevsib;
 		dom_fragment_assign_parent_node(parentNode, fragment);
 		dom_reconcile_ns(doc, newchild);
 	}
@@ -374,17 +398,34 @@ void dom_parent_node_after(dom_object *context, zval *nodes, int nodesc)
 
 void dom_parent_node_before(dom_object *context, zval *nodes, int nodesc)
 {
+	/* Spec link: https://dom.spec.whatwg.org/#dom-childnode-before */
+
 	xmlNode *nextsib = dom_object_get_node(context);
-	xmlNodePtr newchild, prevsib, parentNode;
-	xmlNode *fragment, *afternextsib;
+	xmlNodePtr newchild, parentNode;
+	xmlNode *fragment;
 	xmlDoc *doc;
-	bool beforefirstchild;
 
-	doc = nextsib->doc;
-	prevsib = nextsib->prev;
-	afternextsib = nextsib->next;
+	/* Spec step 1 */
 	parentNode = nextsib->parent;
-	beforefirstchild = !prevsib;
+	/* Spec step 2 */
+	if (!parentNode) {
+		int stricterror = dom_get_strict_error(context->document);
+		php_dom_throw_error(HIERARCHY_REQUEST_ERR, stricterror);
+		return;
+	}
+
+	/* Spec step 3: find first following child not in nodes; otherwise null */
+	xmlNodePtr viable_previous_sibling = nextsib->prev;
+	while (viable_previous_sibling) {
+		if (!dom_is_node_in_list(nodes, nodesc, viable_previous_sibling)) {
+			break;
+		}
+		viable_previous_sibling = viable_previous_sibling->prev;
+	}
+
+	doc = nextsib->doc;
+
+	/* Spec step 4: convert nodes into fragment */
 	fragment = dom_zvals_to_fragment(context->document, parentNode, nodes, nodesc);
 
 	if (fragment == NULL) {
@@ -394,37 +435,14 @@ void dom_parent_node_before(dom_object *context, zval *nodes, int nodesc)
 	newchild = fragment->children;
 
 	if (newchild) {
-		/* first node and last node are both both parameters to DOMElement::before() method so nextsib is null. */
-		if (!parentNode->children) {
-			nextsib = NULL;
-		} else if (beforefirstchild) {
-			/*
-			 * The new node will be inserted before first node, nextsib is first node and afternextsib is last node.
-			 * The first node is not the parameter to DOMElement::before() if parentNode->children == nextsib is true
-			 * and nextsib does not change, otherwise nextsib is the last node.
-			 */
-			nextsib = parentNode->children == nextsib ? nextsib : afternextsib;
-		} else {
-			/*
-			 * The new node will be inserted before last node, prevsib is first node and nestsib is last node.
-			 * The first node is not the parameter to DOMElement::before() if parentNode->children == prevsib is true
-			 * but last node may be, so use prevsib->next to determine the value of nextsib, otherwise nextsib does not change.
-			 */
-			nextsib = parentNode->children == prevsib ? prevsib->next : nextsib;
-		}
-
-		if (parentNode->children == nextsib) {
-			parentNode->children = newchild;
+		/* Step 5: if viable_previous_sibling is null, set it to the parent's first child, otherwise viable_previous_sibling's next sibling */
+		if (!viable_previous_sibling) {
+			viable_previous_sibling = parentNode->children;
 		} else {
-			prevsib->next = newchild;
-		}
-
-		fragment->last->next = nextsib;
-		if (nextsib) {
-			nextsib->prev = fragment->last;
+			viable_previous_sibling = viable_previous_sibling->next;
 		}
-
-		newchild->prev = prevsib;
+		/* Step 6: place fragment into the parent after viable_previous_sibling */
+		dom_pre_insert(viable_previous_sibling, parentNode, newchild, fragment);
 
 		dom_fragment_assign_parent_node(parentNode, fragment);
 		dom_reconcile_ns(doc, newchild);
diff --git a/ext/dom/tests/bug80602.phpt b/ext/dom/tests/bug80602.phpt
index 9f041f686f516..844d829cb08d0 100644
--- a/ext/dom/tests/bug80602.phpt
+++ b/ext/dom/tests/bug80602.phpt
@@ -8,84 +8,84 @@ $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->before($target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "1 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->before($target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "2 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->before($doc->documentElement->lastChild);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "3 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->before($doc->documentElement->firstChild);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "4 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->before($target, $doc->documentElement->lastChild);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "5 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->before($doc->documentElement->lastChild, $target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "6 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->before($target, $doc->documentElement->firstChild);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "7 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->before($doc->documentElement->firstChild, $target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "8 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->before('bar','baz');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "9 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->before('bar','baz');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "10 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->before($target, 'bar','baz');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "11 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->before('bar', $target, 'baz');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "12 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->before('bar', 'baz', $target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "13 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 
@@ -93,19 +93,19 @@ $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->before($target, 'bar','baz');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "14 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->before('bar', $target, 'baz');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "15 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->before('bar', 'baz', $target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "16 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 
@@ -113,21 +113,21 @@ $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->before('bar', $target, $doc->documentElement->lastChild);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "17 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->before($target, 'bar', $doc->documentElement->lastChild);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "18 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->before($target, $doc->documentElement->lastChild, 'bar');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "19 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 
@@ -136,43 +136,43 @@ $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->before('bar', $doc->documentElement->firstChild, $target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "20 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->before($doc->documentElement->firstChild, 'bar', $target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "21 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->before($doc->documentElement->firstChild, $target, 'bar');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "22 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 ?>
 --EXPECTF--
-<a>foo<last/></a>
-<a>foo<last/></a>
-<a><last/>foo</a>
-<a>foo<last/></a>
-<a>foo<last/></a>
-<a><last/>foo</a>
-<a><last/>foo</a>
-<a>foo<last/></a>
-<a>barbazfoo<last/></a>
-<a>foobarbaz<last/></a>
-<a>foobarbaz<last/></a>
-<a>barfoobaz<last/></a>
-<a>barbazfoo<last/></a>
-<a>foo<last/>barbaz</a>
-<a>foobar<last/>baz</a>
-<a>foobarbaz<last/></a>
-<a>barfoo<last/></a>
-<a>foobar<last/></a>
-<a>foo<last/>bar</a>
-<a>barfoo<last/></a>
-<a>foobar<last/></a>
-<a>foo<last/>bar</a>
+1 <a>foo<last/></a>
+2 <a>foo<last/></a>
+3 <a><last/>foo</a>
+4 <a>foo<last/></a>
+5 <a>foo<last/></a>
+6 <a><last/>foo</a>
+7 <a><last/>foo</a>
+8 <a>foo<last/></a>
+9 <a>barbazfoo<last/></a>
+10 <a>foobarbaz<last/></a>
+11 <a>foobarbaz<last/></a>
+12 <a>barfoobaz<last/></a>
+13 <a>barbazfoo<last/></a>
+14 <a>foo<last/>barbaz</a>
+15 <a>foobar<last/>baz</a>
+16 <a>foobarbaz<last/></a>
+17 <a>barfoo<last/></a>
+18 <a>foobar<last/></a>
+19 <a>foo<last/>bar</a>
+20 <a>barfoo<last/></a>
+21 <a>foobar<last/></a>
+22 <a>foo<last/>bar</a>
diff --git a/ext/dom/tests/bug80602_2.phpt b/ext/dom/tests/bug80602_2.phpt
index 1151417c0f845..7c5070f51424c 100644
--- a/ext/dom/tests/bug80602_2.phpt
+++ b/ext/dom/tests/bug80602_2.phpt
@@ -8,84 +8,84 @@ $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->after($target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "1 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->after($target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "2 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->after($doc->documentElement->lastChild);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "3 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->after($doc->documentElement->firstChild);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "4 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->after($target, $doc->documentElement->lastChild);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "5 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->after($doc->documentElement->lastChild, $target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "6 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->after($target, $doc->documentElement->firstChild);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "7 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->after($doc->documentElement->firstChild, $target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "8 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->after('bar','baz');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "9 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->after('bar','baz');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "10 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->after($target, 'bar','baz');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "11 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->after('bar', $target, 'baz');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "12 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->after('bar', 'baz', $target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "13 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 
@@ -93,19 +93,19 @@ $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->after($target, 'bar','baz');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "14 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->after('bar', $target, 'baz');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "15 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->after('bar', 'baz', $target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "16 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 
@@ -113,21 +113,21 @@ $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->after('bar', $target, $doc->documentElement->lastChild);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "17 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->after($target, 'bar', $doc->documentElement->lastChild);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "18 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->firstChild;
 $target->after($target, $doc->documentElement->lastChild, 'bar');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "19 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 
@@ -136,43 +136,43 @@ $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->after('bar', $doc->documentElement->firstChild, $target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "20 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->after($doc->documentElement->firstChild, 'bar', $target);
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "21 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 
 $doc = new \DOMDocument();
 $doc->loadXML('<a>foo<last/></a>');
 $target = $doc->documentElement->lastChild;
 $target->after($doc->documentElement->firstChild, $target, 'bar');
-echo $doc->saveXML($doc->documentElement).PHP_EOL;
+echo "22 ", $doc->saveXML($doc->documentElement).PHP_EOL;
 
 ?>
 --EXPECTF--
-<a>foo<last/></a>
-<a>foo<last/></a>
-<a>foo<last/></a>
-<a><last/>foo</a>
-<a>foo<last/></a>
-<a><last/>foo</a>
-<a><last/>foo</a>
-<a>foo<last/></a>
-<a>foobarbaz<last/></a>
-<a>foo<last/>barbaz</a>
-<a>foobarbaz<last/></a>
-<a>barfoobaz<last/></a>
-<a>barbazfoo<last/></a>
-<a>foo<last/>barbaz</a>
-<a>foobar<last/>baz</a>
-<a>foobarbaz<last/></a>
-<a>barfoo<last/></a>
-<a>foobar<last/></a>
-<a>foo<last/>bar</a>
-<a>barfoo<last/></a>
-<a>foobar<last/></a>
-<a>foo<last/>bar</a>
+1 <a>foo<last/></a>
+2 <a>foo<last/></a>
+3 <a>foo<last/></a>
+4 <a><last/>foo</a>
+5 <a>foo<last/></a>
+6 <a><last/>foo</a>
+7 <a><last/>foo</a>
+8 <a>foo<last/></a>
+9 <a>foobarbaz<last/></a>
+10 <a>foo<last/>barbaz</a>
+11 <a>foobarbaz<last/></a>
+12 <a>barfoobaz<last/></a>
+13 <a>barbazfoo<last/></a>
+14 <a>foo<last/>barbaz</a>
+15 <a>foobar<last/>baz</a>
+16 <a>foobarbaz<last/></a>
+17 <a>barfoo<last/></a>
+18 <a>foobar<last/></a>
+19 <a>foo<last/>bar</a>
+20 <a>barfoo<last/></a>
+21 <a>foobar<last/></a>
+22 <a>foo<last/>bar</a>
diff --git a/ext/dom/tests/bug80602_3.phpt b/ext/dom/tests/bug80602_3.phpt
new file mode 100644
index 0000000000000..f9bf67e778da5
--- /dev/null
+++ b/ext/dom/tests/bug80602_3.phpt
@@ -0,0 +1,120 @@
+--TEST--
+Bug #80602 (Segfault when using DOMChildNode::before()) - use-after-free variation
+--FILE--
+<?php
+
+$doc = new \DOMDocument();
+$doc->loadXML('<a>foo<last/></a>');
+$target = $doc->documentElement->lastChild;
+$target->before('bar', $doc->documentElement->firstChild, 'baz');
+echo $doc->saveXML($doc->documentElement), "\n";
+var_dump($target);
+
+$doc = new \DOMDocument();
+$doc->loadXML('<a>foo<last/></a>');
+$target = $doc->documentElement->lastChild;
+// Note: after instead of before
+$target->after('bar', $doc->documentElement->firstChild, 'baz');
+echo $doc->saveXML($doc->documentElement), "\n";
+var_dump($target);
+
+?>
+--EXPECTF--
+<a>barfoobaz<last/></a>
+object(DOMElement)#3 (23) {
+  ["schemaTypeInfo"]=>
+  NULL
+  ["tagName"]=>
+  string(4) "last"
+  ["firstElementChild"]=>
+  NULL
+  ["lastElementChild"]=>
+  NULL
+  ["childElementCount"]=>
+  int(0)
+  ["previousElementSibling"]=>
+  NULL
+  ["nextElementSibling"]=>
+  NULL
+  ["nodeName"]=>
+  string(4) "last"
+  ["nodeValue"]=>
+  string(0) ""
+  ["nodeType"]=>
+  int(1)
+  ["parentNode"]=>
+  string(22) "(object value omitted)"
+  ["childNodes"]=>
+  string(22) "(object value omitted)"
+  ["firstChild"]=>
+  NULL
+  ["lastChild"]=>
+  NULL
+  ["previousSibling"]=>
+  string(22) "(object value omitted)"
+  ["nextSibling"]=>
+  NULL
+  ["attributes"]=>
+  string(22) "(object value omitted)"
+  ["ownerDocument"]=>
+  string(22) "(object value omitted)"
+  ["namespaceURI"]=>
+  NULL
+  ["prefix"]=>
+  string(0) ""
+  ["localName"]=>
+  string(4) "last"
+  ["baseURI"]=>
+  string(%d) %s
+  ["textContent"]=>
+  string(0) ""
+}
+<a><last/>barfoobaz</a>
+object(DOMElement)#2 (23) {
+  ["schemaTypeInfo"]=>
+  NULL
+  ["tagName"]=>
+  string(4) "last"
+  ["firstElementChild"]=>
+  NULL
+  ["lastElementChild"]=>
+  NULL
+  ["childElementCount"]=>
+  int(0)
+  ["previousElementSibling"]=>
+  NULL
+  ["nextElementSibling"]=>
+  NULL
+  ["nodeName"]=>
+  string(4) "last"
+  ["nodeValue"]=>
+  string(0) ""
+  ["nodeType"]=>
+  int(1)
+  ["parentNode"]=>
+  string(22) "(object value omitted)"
+  ["childNodes"]=>
+  string(22) "(object value omitted)"
+  ["firstChild"]=>
+  NULL
+  ["lastChild"]=>
+  NULL
+  ["previousSibling"]=>
+  NULL
+  ["nextSibling"]=>
+  string(22) "(object value omitted)"
+  ["attributes"]=>
+  string(22) "(object value omitted)"
+  ["ownerDocument"]=>
+  string(22) "(object value omitted)"
+  ["namespaceURI"]=>
+  NULL
+  ["prefix"]=>
+  string(0) ""
+  ["localName"]=>
+  string(4) "last"
+  ["baseURI"]=>
+  string(%d) %s
+  ["textContent"]=>
+  string(0) ""
+}
diff --git a/ext/dom/tests/bug80602_4.phpt b/ext/dom/tests/bug80602_4.phpt
new file mode 100644
index 0000000000000..a1df8d10caa31
--- /dev/null
+++ b/ext/dom/tests/bug80602_4.phpt
@@ -0,0 +1,33 @@
+--TEST--
+Bug #80602 (Segfault when using DOMChildNode::before()) - after text merge variation
+--FILE--
+<?php
+
+$doc = new \DOMDocument();
+$doc->loadXML('<a>foo<last/>bar</a>');
+$foo = $doc->firstChild->firstChild;
+$bar = $doc->firstChild->lastChild;
+
+$foo->after($bar);
+
+var_dump($doc->saveXML());
+
+$foo->nodeValue = "x";
+
+var_dump($doc->saveXML());
+
+$bar->nodeValue = "y";
+
+var_dump($doc->saveXML());
+
+?>
+--EXPECT--
+string(43) "<?xml version="1.0"?>
+<a>foobar<last/></a>
+"
+string(41) "<?xml version="1.0"?>
+<a>xbar<last/></a>
+"
+string(39) "<?xml version="1.0"?>
+<a>xy<last/></a>
+"
diff --git a/ext/dom/tests/gh11288.phpt b/ext/dom/tests/gh11288.phpt
new file mode 100644
index 0000000000000..f70bea80d9085
--- /dev/null
+++ b/ext/dom/tests/gh11288.phpt
@@ -0,0 +1,67 @@
+--TEST--
+GH-11288 (Error: Couldn't fetch DOMElement introduced in 8.2.6, 8.1.19)
+--FILE--
+<?php
+$html = <<<HTML
+<!DOCTYPE HTML>
+<html>
+<span class="unwrap_me"><i><span class="foo">Lorem</span></i><span class="foo">ipsum</span></span>
+</html>
+HTML;
+
+$dom = new DOMDocument();
+$dom->loadHTML($html);
+
+$spans = iterator_to_array($dom->getElementsByTagName('span')->getIterator());
+foreach ($spans as $span) {
+    if ('unwrap_me' === $span->getAttribute('class')) {
+        $fragment = $dom->createDocumentFragment();
+        $fragment->append(...$span->childNodes);
+        $span->parentNode?->replaceChild($fragment, $span);
+    }
+}
+
+var_dump(str_replace("\n", "", $dom->saveHTML()));
+
+$html = <<<HTML
+<!DOCTYPE HTML>
+<html>
+<span class="unwrap_me"><i><span class="foo">Lorem</span></i><span class="foo">ipsum</span></span>
+</html>
+HTML;
+
+$dom = new DOMDocument();
+$dom->loadHTML($html);
+
+$spans = iterator_to_array($dom->getElementsByTagName('span')->getIterator());
+foreach ($spans as $span) {
+    if ('unwrap_me' === $span->getAttribute('class')) {
+        $span->replaceWith(...$span->childNodes);
+    }
+}
+
+var_dump(str_replace("\n", "", $dom->saveHTML()));
+
+$html = <<<HTML
+<!DOCTYPE HTML>
+<html>
+<span class="unwrap_me"><i><span class="foo">Lorem</span></i><span class="foo">ipsum</span></span>
+</html>
+HTML;
+
+$dom = new DOMDocument();
+$dom->loadHTML($html);
+
+$spans = iterator_to_array($dom->getElementsByTagName('span')->getIterator());
+foreach ($spans as $span) {
+    if ('unwrap_me' === $span->getAttribute('class')) {
+        $span->replaceWith('abc');
+    }
+}
+
+var_dump(str_replace("\n", "", $dom->saveHTML()));
+?>
+--EXPECT--
+string(108) "<!DOCTYPE HTML><html><body><i><span class="foo">Lorem</span></i><span class="foo">ipsum</span></body></html>"
+string(108) "<!DOCTYPE HTML><html><body><i><span class="foo">Lorem</span></i><span class="foo">ipsum</span></body></html>"
+string(44) "<!DOCTYPE HTML><html><body>abc</body></html>"
diff --git a/ext/dom/tests/gh11289.phpt b/ext/dom/tests/gh11289.phpt
new file mode 100644
index 0000000000000..7771a486bd66b
--- /dev/null
+++ b/ext/dom/tests/gh11289.phpt
@@ -0,0 +1,28 @@
+--TEST--
+GH-11289 (DOMException: Not Found Error introduced in 8.2.6, 8.1.19)
+--FILE--
+<?php
+
+$html = <<<HTML
+<!DOCTYPE HTML>
+<html>
+<body>
+    <div></div>
+</body>
+</html>
+HTML;
+
+$dom = new DOMDocument();
+$dom->loadHTML($html);
+
+$divs = iterator_to_array($dom->getElementsByTagName('div')->getIterator());
+foreach ($divs as $div) {
+    $fragment = $dom->createDocumentFragment();
+    $fragment->appendXML('<p>Hi!</p>');
+    $div->replaceWith(...$fragment->childNodes);
+}
+
+var_dump(str_replace("\n", "", $dom->saveHTML()));
+?>
+--EXPECT--
+string(55) "<!DOCTYPE HTML><html><body>    <p>Hi!</p></body></html>"
diff --git a/ext/dom/tests/gh11290.phpt b/ext/dom/tests/gh11290.phpt
new file mode 100644
index 0000000000000..2900720301041
--- /dev/null
+++ b/ext/dom/tests/gh11290.phpt
@@ -0,0 +1,27 @@
+--TEST--
+GH-11290 (DOMElement::replaceWith causes crash)
+--FILE--
+<?php
+$html = <<<HTML
+<!DOCTYPE HTML>
+<html>
+<body>
+    <p><span class="unwrap_me">Lorem</span><span class="unwrap_me">ipsum</span><span class="unwrap_me">dolor</span></p>
+</body>
+</html>
+HTML;
+
+$dom = new DOMDocument();
+$dom->loadHTML($html);
+
+$spans = iterator_to_array($dom->getElementsByTagName('span')->getIterator());
+foreach ($spans as $span) {
+    if ('unwrap_me' === $span->getAttribute('class')) {
+        $span->replaceWith(...$span->childNodes);
+    }
+}
+
+var_dump(str_replace("\n", "", $dom->saveHTML()));
+?>
+--EXPECT--
+string(67) "<!DOCTYPE HTML><html><body>    <p>Loremipsumdolor</p></body></html>"
diff --git a/ext/dom/tests/gh9142.phpt b/ext/dom/tests/gh9142.phpt
new file mode 100644
index 0000000000000..f72dfa823f38c
--- /dev/null
+++ b/ext/dom/tests/gh9142.phpt
@@ -0,0 +1,20 @@
+--TEST--
+GH-9142 (DOMChildNode replaceWith() double-free error when replacing elements not separated by any whitespace)
+--FILE--
+<?php
+
+$document = '<var>One</var><var>Two</var>';
+
+($dom = new DOMDocument('1.0', 'UTF-8'))->loadHTML($document);
+
+foreach ((new DOMXPath($dom))->query('//var') as $var) {
+    $var->replaceWith($dom->createElement('p', $var->nodeValue));
+}
+
+var_dump($dom->saveHTML());
+
+?>
+--EXPECT--
+string(154) "<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
+<html><body><p>One</p><p>Two</p></body></html>
+"