Add edge-case testcase for offset in DOMNamedNodeMap

Author: nielsdos

ext/dom/tests/DOMNamedNodeMap_edge_case_offset.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Test edge case offsets in DOMNamedNodeMap
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$document = new DomDocument();
+$root = $document->createElement('root');
+$document->appendChild($root);
+$root->setAttribute('attrib', 'value');
+var_dump($root->attributes->length);
+// Consistent with the method call
+try {
+    var_dump($root->attributes[-1]);
+} catch (ValueError $e) {
+    echo $e->getMessage(), "\n";
+}
+try {
+    $root->attributes[][] = null;
+} catch (Throwable $e) {
+    echo $e->getMessage(), "\n";
+}
+
+?>
+--EXPECT--
+int(1)
+must be between 0 and 2147483647
+Cannot access DOMNamedNodeMap without offset