Neutralize php2shell at the Ingestion Tier.

# Local keep-alive pool to isolated PHP 5.3 backend
upstream legacy_backend_pool {
    server 10.0.1.50:80;
    keepalive 32;
}

server {
    listen 127.0.0.1:8081;
    server_name _;

    location / {
        proxy_pass http://legacy_backend_pool;
        proxy_http_version 1.1;
        proxy_set_header Connection "";
        proxy_set_header Host $http_host;
        proxy_set_header X-Forwarded-For $remote_addr;
        proxy_buffering off;
    }
}

// Run IDS inspection before proxying
$ids = new GatewayIDS();
$ids->inspectRequest($_SERVER, $_GET, $_POST, $_COOKIE);

// Native stream context over persistent pool
$context = stream_context_create([
    'http' => [
        'method'  => $_SERVER['REQUEST_METHOD'],
        'header'  => $sanitizedHeaders,
        'content' => file_get_contents('php://input'),
        'timeout' => 15,
        'ignore_errors' => true,
    ]
]);

$response = file_get_contents('http://127.0.0.1:8081' . $uri, false, $context);
echo $response;