Null type issue

src/PurplePixie/PhpDns/DNSQuery.php

@@ -59,6 +59,8 @@ class DNSQuery
 
     private bool $connectionException = false;
 
+    private bool $responseException = false;
+
     public function __construct(string $server, int $port = 53, int $timeout = 60, bool $udp = true, bool $debug = false, bool $binarydebug = false)
     {
         $this->server = $server;
@@ -188,7 +190,7 @@ private function clearError(): void
 
     /**
      * @return array
-     * @throws Exceptions\InvalidQueryTypeId
+     * @throws Exceptions\InvalidQueryTypeId|Exceptions\InvalidResponse
      */
     private function readRecord(): array
     {
@@ -198,13 +200,32 @@ private function readRecord(): array
 
         $ans_header_bin = $this->readResponse(10); // 10 byte header
 
-        $ans_header = unpack('ntype/nclass/Nttl/nlength', $ans_header_bin);
+        $ans_header = @unpack('ntype/nclass/Nttl/nlength', $ans_header_bin);
 
-        if (is_array($ans_header)) $this->debug(
-            'Record Type ' . $ans_header['type'] . ' Class ' . $ans_header['class'] .
-            ' TTL ' . $ans_header['ttl'] . ' Length ' . $ans_header['length']
-        );
-        else $this->debug("Error unpacking answer header, no array returned.");
+        if ($ans_header === null || $ans_header === false || !is_array($ans_header)) // the unpack has failed - we assume an invalid return
+        {
+            $this->debug("Error unpacking answer header, no array returned.");
+
+            if ($this->responseException)
+                throw new Exceptions\InvalidResponse("Answer header invalid format or empty");
+
+            return [
+                'header' => [],
+                'typeid' => null,
+                'typename' => "",
+                'data'   => "",
+                'domain' => "",
+                'string' => "Error unpacking answer header",
+                'extras' => "",
+            ];
+        }
+        else
+        {
+            $this->debug(
+                'Record Type ' . $ans_header['type'] . ' Class ' . $ans_header['class'] .
+                ' TTL ' . $ans_header['ttl'] . ' Length ' . $ans_header['length']
+            );
+        }
 
         $typeId = $ans_header['type'];
 
@@ -767,4 +788,14 @@ public function setConnectionException(bool $value): void
     {
         $this->connectionException = $value;
     }
+
+    public function setResponseException(bool $value): void
+    {
+        $this->responseException = $value;
+    }
+
+    public function getResponseException(): bool
+    {
+        return $this->responseException;
+    }
 }

src/PurplePixie/PhpDns/Exceptions/InvalidResponse.php

@@ -0,0 +1,29 @@
+<?php
+
+/**
+ * Copyright (C) 2025, David Cutting, Purplepixie Systems
+ *
+ * This is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * The software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this software.  If not, see www.gnu.org/licenses
+ *
+ * For more information see www.purplepixie.org/phpdns
+ */
+
+namespace PurplePixie\PhpDns\Exceptions;
+
+class InvalidResponse extends \Exception {
+
+    public function __construct(string $message) {
+        parent::__construct('Invalid response: ' . $message);
+    }
+}