use mb_ functions in GelfFormatter

src/Monolog/Formatter/GelfMessageFormatter.php

@@ -93,10 +93,10 @@ class GelfMessageFormatter extends NormalizerFormatter
             ->setLevel($this->logLevels[$record['level']]);
 
         // message length + system name length + 200 for padding / metadata
-        $len = 200 + strlen((string) $record['message']) + strlen($this->systemName);
+        $len = 200 + mb_strlen((string) $record['message']) + mb_strlen($this->systemName);
 
         if ($len > $this->maxLength) {
-            $message->setShortMessage(substr($record['message'], 0, $this->maxLength));
+            $message->setShortMessage(mb_substr($record['message'], 0, $this->maxLength));
         }
 
         if (isset($record['channel'])) {
@@ -113,9 +113,9 @@ class GelfMessageFormatter extends NormalizerFormatter
 
         foreach ($record['extra'] as $key => $val) {
             $val = is_scalar($val) || null === $val ? $val : $this->toJson($val);
-            $len = strlen($this->extraPrefix . $key . $val);
+            $len = mb_strlen($this->extraPrefix . $key . $val);
             if ($len > $this->maxLength) {
-                $message->setAdditional($this->extraPrefix . $key, substr($val, 0, $this->maxLength));
+                $message->setAdditional($this->extraPrefix . $key, mb_substr($val, 0, $this->maxLength));
                 continue;
             }
             $message->setAdditional($this->extraPrefix . $key, $val);
@@ -123,9 +123,9 @@ class GelfMessageFormatter extends NormalizerFormatter
 
         foreach ($record['context'] as $key => $val) {
             $val = is_scalar($val) || null === $val ? $val : $this->toJson($val);
-            $len = strlen($this->contextPrefix . $key . $val);
+            $len = mb_strlen($this->contextPrefix . $key . $val);
             if ($len > $this->maxLength) {
-                $message->setAdditional($this->contextPrefix . $key, substr($val, 0, $this->maxLength));
+                $message->setAdditional($this->contextPrefix . $key, mb_substr($val, 0, $this->maxLength));
                 continue;
             }
             $message->setAdditional($this->contextPrefix . $key, $val);

tests/Monolog/Formatter/GelfMessageFormatterTest.php

@@ -251,6 +251,26 @@ class GelfMessageFormatterTest extends \PHPUnit\Framework\TestCase
         $this->assertGreaterThanOrEqual(131289, $length, 'The message should not be truncated');
     }
 
+    public function testFormatWithLargeCyrillicData()
+    {
+        $formatter = new GelfMessageFormatter();
+        $record = [
+            'level' => Logger::ERROR,
+            'level_name' => 'ERROR',
+            'channel' => 'meh',
+            'context' => ['exception' => str_repeat('а', 32767)],
+            'datetime' => new \DateTimeImmutable("@0"),
+            'extra' => ['key' => str_repeat('б', 32767)],
+            'message' => str_repeat('в', 32767),
+        ];
+        $message = $formatter->format($record);
+        $messageArray = $message->toArray();
+
+        $messageString = json_encode($messageArray);
+
+        $this->assertIsString($messageString);
+    }
+
     private function isLegacy()
     {
         return interface_exists('\Gelf\IMessagePublisher');