Merge pull request #2463 from kylekatarnls/fix/php-8.1

Document bug 81458

src/Carbon/Traits/Difference.php

@@ -124,10 +124,10 @@ public function diff($date = null, $absolute = false)
     {
         $other = $this->resolveCarbon($date);
 
-        // Can be removed if https://github.com/derickr/timelib/pull/110
-        // is merged
-        // https://bugs.php.net/bug.php?id=80998 was announced fixed in PHP 8.1.0beta3
-        // but created a reverse-regression when using UTC, so we still need this hack
+        // Work-around for https://bugs.php.net/bug.php?id=81458
+        // It was initially introduced for https://bugs.php.net/bug.php?id=80998
+        // The very specific case of 80998 was fixed in PHP 8.1beta3, but it introduced 81458
+        // So we still need to keep this for now
         // @codeCoverageIgnoreStart
         if (version_compare(PHP_VERSION, '8.1.0-dev', '>=') && $other->tz !== $this->tz) {
             $other = $other->avoidMutation()->tz($this->tz);

tests/Carbon/IsTest.php

@@ -976,6 +976,11 @@ public function getFormatLetters(): Generator
     public function testHasFormatWithSingleLetter($letter)
     {
         $output = Carbon::now()->format($letter);
+
+        if ($output === '1000' && $letter === 'v' && version_compare(PHP_VERSION, '7.2.12', '<')) {
+            $output = '000';
+        }
+
         $this->assertTrue(Carbon::hasFormat($output, $letter), "'$letter' format should match '$output'");
     }
 

tests/CarbonImmutable/IsTest.php

@@ -963,6 +963,11 @@ public function getFormatLetters(): Generator
     public function testHasFormatWithSingleLetter($letter)
     {
         $output = Carbon::now()->format($letter);
+
+        if ($output === '1000' && $letter === 'v' && version_compare(PHP_VERSION, '7.2.12', '<')) {
+            $output = '000';
+        }
+
         $this->assertTrue(Carbon::hasFormat($output, $letter), "'$letter' format should match '$output'");
     }