Avoid PHP 8.5 deprecation notice when loading the tracker

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 This is the Developer Changelog for Matomo PHP Tracker. All breaking changes or new features are listed below.
 
+## Matomo PHP Tracker 4.0.1
+
+### Fixed
+- Loading `MatomoTracker.php` no longer emits a deprecation notice for the predefined `$http_response_header` variable on PHP 8.5. PHP reports it at compile time, so it was emitted on every include (#155).
+
 ## Matomo PHP Tracker 4.0.0
 
 Attention: this is a major release with breaking changes.

MatomoTracker.php

@@ -2400,6 +2400,12 @@ protected function sendRequest(#[\SensitiveParameter] string $url, string $metho
             $stream_options = $this->prepareStreamOptions($method, $data, $forcePostUrlEncoded);
 
             $ctx = stream_context_create($stream_options);
+
+            // $http_response_header must be assigned before the fallback read below: PHP 8.5
+            // deprecated the predefined variable and reports it at compile time, so the read would
+            // otherwise emit a notice merely by loading this file. PHP still overwrites the value.
+            $http_response_header = [];
+
             $response = @file_get_contents($url, false, $ctx);
             if ($response === false && $this->exceptionsEnabled) {
                 // Only include the host (never the query string, which carries token_auth/PII) in the message.
@@ -2414,8 +2420,8 @@ protected function sendRequest(#[\SensitiveParameter] string $url, string $metho
                     $responseHeaders = $headers;
                 }
             } elseif ($response !== false) {
-                // PHP populates $http_response_header in the local scope whenever an HTTP response
-                // was received; the $response !== false guard guarantees that is the case here.
+                // PHP < 8.5 has no http_get_last_response_headers() and populates the local
+                // variable instead, which it only does when a response was actually received.
                 $responseHeaders = $http_response_header;
             }
 

tests/Unit/MatomoTrackerTest.php

@@ -546,6 +546,29 @@ public function testStreamTransportFailSafeReturnsFalseWhenExceptionsDisabled():
         $this->assertFalse($tracker->doTrackPageView('some title'));
     }
 
+    /**
+     * Loading the tracker must not emit any notice, as tools that turn those into exceptions
+     * (e.g. Psalm) would abort while autoloading the class. This is what the `$http_response_header`
+     * assignment in `sendRequest()` guards, so that assignment must stay above the read following it.
+     */
+    public function testLoadingTheTrackerEmitsNoDeprecationNotice(): void
+    {
+        // -n ignores the environment's php.ini, so that unrelated startup diagnostics (e.g. a
+        // dangling extension line) cannot fail this test
+        $command = escapeshellarg(PHP_BINARY)
+            . ' -n -d error_reporting=-1 -d display_errors=1 -d log_errors=0 -r '
+            . escapeshellarg('include ' . var_export(dirname(__DIR__, 2) . '/MatomoTracker.php', true) . '; echo \'loaded\';')
+            . ' 2>&1';
+
+        $output = [];
+        $exitCode = -1;
+        exec($command, $output, $exitCode);
+
+        // expecting the marker rather than just no output also catches a child that never ran
+        $this->assertSame('loaded', trim(implode("\n", $output)), 'Loading the tracker must not emit any notice');
+        $this->assertSame(0, $exitCode);
+    }
+
     public function testGetUrlTrackCrash(): void
     {
         $tracker = $this->createTracker();