Merge pull request #529 from nerg4l/fix/string-length

Use correct method for string length

src/Http/CurlDispatcher.php

@@ -210,7 +210,7 @@ private function writeBody($curl, $string): int
         }
 
         if ($this->body->getSize() > self::$contentLengthThreshold) {
-            return count($string);
+            return strlen($string);
         }
 
         return $this->body->write($string);