getHandlerList(); $list->appendBuild(Middleware::mapRequest(function (RequestInterface $req) use($agentString) { if (!empty($req->getHeader('User-Agent')) && !empty($req->getHeader('User-Agent')[0])) { $userAgent = $req->getHeader('User-Agent')[0]; if (\strpos($userAgent, $agentString) === \false) { $userAgent .= " {$agentString}"; } } else { $userAgent = $agentString; } $req = $req->withHeader('User-Agent', $userAgent); return $req; })); } }