[HttpFoundation] Fix dumping array cookies

Author: nicolas-grekas

Request.php

@@ -522,10 +522,10 @@ public function __toString()
         $cookies = [];
 
         foreach ($this->cookies as $k => $v) {
-            $cookies[] = $k.'='.$v;
+            $cookies[] = \is_array($v) ? http_build_query([$k => $v], '', '; ', \PHP_QUERY_RFC3986) : "$k=$v";
         }
 
-        if (!empty($cookies)) {
+        if ($cookies) {
             $cookieHeader = 'Cookie: '.implode('; ', $cookies)."\r\n";
         }
 

Tests/RequestTest.php

@@ -1702,6 +1702,12 @@ public function testToString()
         $asString = (string) $request;
 
         $this->assertStringContainsString('Cookie: Foo=Bar; Another=Cookie', $asString);
+
+        $request->cookies->set('foo.bar', [1, 2]);
+
+        $asString = (string) $request;
+
+        $this->assertStringContainsString('foo.bar%5B0%5D=1; foo.bar%5B1%5D=2', $asString);
     }
 
     public function testIsMethod()