Ensure headers are consistent

[akrabat]

• Ensure that our headers implementation is completely compliant with PSR-7
• Ensure that getHeader() and getHeaders() are consistent. See GetHeaders and GetHeader have a different result Slim#2400

Migrated from slimphp/Slim-Http#61

[schmengler]

Glad that the issue is being addressed. This caused me some headache when passing a modified Slim request object from the environment to a Guzzle client and the headers with HTTP_ prefix got lost.

A workaround is to reset the original keys, using reflection:

    private function resetHeaderOriginalKeys(Request $request): void
    {
        $headersProperty = new \ReflectionProperty(Request::class, 'headers');
        $headersProperty->setAccessible(true);
        /** @var Headers $headers */
        $headers = $headersProperty->getValue($request);
        foreach ($headers as $key => $header) {
            $headers->set($key, $header['value']);
        }
        $headersProperty->setAccessible(false);
    }

[sridesmet]

Glad that the issue is being addressed. This caused me some headache when passing a modified Slim request object from the environment to a Guzzle client and the headers with HTTP_ prefix got lost.

A workaround is to reset the original keys, using reflection:

    private function resetHeaderOriginalKeys(Request $request): void
    {
        $headersProperty = new \ReflectionProperty(Request::class, 'headers');
        $headersProperty->setAccessible(true);
        /** @var Headers $headers */
        $headers = $headersProperty->getValue($request);
        foreach ($headers as $key => $header) {
            $headers->set($key, $header['value']);
        }
        $headersProperty->setAccessible(false);
    }

Here is your code in a middleware: https://gist.github.com/sridesmet/a3e0a6f3a3515aaf5d5b4b42479e8c67