I want to get the number of seconds an http request takes. I have this code:

$starttime = microtime(true);

$response = $this->httpClient->request(
    'POST',
    $endpoint,
    [
        'headers' => $header,
        'body' => $inputXml
    ]
);

sleep(2);
$endtime = microtime(true);
$timeDiffInSeconds = ($endtime - $starttime);

the request takes around 3 seconds, plus the sleep time, in postman I see 5,08s, that looks correct. But in PHP I $timeDiffInSeconds is float(2.0008609294891).

is http client async?, how can I see the real execution time?.
is there a parameter in the http client that shows the time it took?