Fix bug #32755 Segfault in replaceChild() when DocumentFragment has no children

update test

ext/dom/node.c

@@ -1134,7 +1134,9 @@ PHP_FUNCTION(dom_node_replace_child)
 			xmlUnlinkNode(oldchild);
 
 			newchild = _php_dom_insert_fragment(nodep, prevsib, nextsib, newchild, intern, newchildobj TSRMLS_CC);
-			dom_reconcile_ns(nodep->doc, newchild);
+			if (newchild) {
+				dom_reconcile_ns(nodep->doc, newchild);
+			}
 		} else if (oldchild != newchild) {
 			if (newchild->doc == NULL && nodep->doc != NULL) {
 				xmlSetTreeDoc(newchild, nodep->doc);

ext/dom/tests/bug32615.phpt

@@ -62,6 +62,12 @@ $frag->appendChild(new DOMElement('second'));
 $frag->appendChild(new DOMElement('third'));
 $root->insertBefore($frag, $node);
 
+echo $dom->saveXML()."\n";
+
+$frag = $dom->createDocumentFragment();
+$root = $dom->documentElement;
+$root->replaceChild($frag, $root->firstChild);
+
 echo $dom->saveXML();
 
 ?>
@@ -73,3 +79,6 @@ echo $dom->saveXML();
 <?xml version="1.0"?>
 <root><first/><second/><third/><fourth/></root>
 
+<?xml version="1.0"?>
+<root><second/><third/><fourth/></root>
+