merged branch pborreli/patch-9 (PR #7943)

This PR was merged into the master branch.

Discussion
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[HttpFoundation] Reverted a part of #7931

refs: #7931

Commits
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09c2114 Reverted a part of f5e7f24

src/Symfony/Component/HttpFoundation/ServerBag.php

@@ -30,7 +30,7 @@ public function getHeaders()
         $headers = array();
         $contentHeaders = array('CONTENT_LENGTH' => true, 'CONTENT_MD5' => true, 'CONTENT_TYPE' => true);
         foreach ($this->parameters as $key => $value) {
-            if ('HTTP_' === substr($key, 0, 5)) {
+            if (0 === strpos($key, 'HTTP_')) {
                 $headers[substr($key, 5)] = $value;
             }
             // CONTENT_* are not prefixed with HTTP_