The multipart/form-data uses the UTF-8 charset by default

Author: natanfelles

src/Request.php

@@ -147,7 +147,7 @@ protected function getMultipartBody() : string
         $boundary = \str_repeat('-', 24) . \substr(\md5(\implode("\r\n", $bodyParts)), 0, 16);
         $this->setHeader(
             RequestHeader::CONTENT_TYPE,
-            'multipart/form-data; charset=UTF-8; boundary=' . $boundary
+            'multipart/form-data; boundary=' . $boundary
         );
         foreach ($bodyParts as &$part) {
             $part = "--{$boundary}\r\n{$part}";
@@ -384,7 +384,7 @@ public function setFiles(array $files) : static
     {
         if ($files) {
             $this->tryUpgradeFromGetToPost();
-            $this->setContentType('multipart/form-data');
+            $this->setContentType('multipart/form-data', null);
         }
         $this->files = $files;
         return $this;

tests/RequestTest.php

@@ -127,7 +127,7 @@ public function testFiles() : void
         self::assertNull($this->request->getHeader('content-type'));
         $this->request->setFiles(['upload' => __FILE__]);
         self::assertSame(
-            'multipart/form-data; charset=UTF-8',
+            'multipart/form-data',
             $this->request->getHeader('content-type')
         );
         self::assertTrue($this->request->hasFiles());
@@ -252,7 +252,7 @@ public function testToStringMultipart() : void
         ]);
         $message = (string) $request;
         self::assertStringContainsString(
-            'Content-Type: multipart/form-data; charset=UTF-8; boundary=',
+            'Content-Type: multipart/form-data; boundary=',
             $message
         );
         self::assertStringContainsString(