From a69cf15e51cd1e42b5a34d448cc053a772ad05f5 Mon Sep 17 00:00:00 2001
From: ivelin vasilev <i.d.vasilevv@gmail.com>
Date: Thu, 8 May 2025 01:06:34 +0300
Subject: [PATCH] [HttpFoundation] Emit PHP warning when
 Response::sendHeaders() while output has already been sent

---
 src/Symfony/Component/HttpFoundation/Response.php | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/Symfony/Component/HttpFoundation/Response.php b/src/Symfony/Component/HttpFoundation/Response.php
index 638b5bf601347..6766f2c77099e 100644
--- a/src/Symfony/Component/HttpFoundation/Response.php
+++ b/src/Symfony/Component/HttpFoundation/Response.php
@@ -317,6 +317,11 @@ public function sendHeaders(?int $statusCode = null): static
     {
         // headers have already been sent by the developer
         if (headers_sent()) {
+            if (!\in_array(\PHP_SAPI, ['cli', 'phpdbg', 'embed'], true)) {
+                $statusCode ??= $this->statusCode;
+                header(\sprintf('HTTP/%s %s %s', $this->version, $statusCode, $this->statusText), true, $statusCode);
+            }
+
             return $this;
         }