Google Recaptcha verify

grecaptcha.php

<?php
$ch = curl_init();
if ($ch === false) {
    user_error("curl_init fail");
}
$opt = 1;
$opt &= curl_setopt($ch, CURLOPT_URL, "https://www.google.com/recaptcha/api/siteverify");
$opt &= curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$opt &= curl_setopt($ch, CURLOPT_TIMEOUT, 3);
$opt &= curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 3);
$opt &= curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query([
    "secret" => "SUPERSECRETHERE",
    "response" => $input->g_recaptcha_response,
    "remoteip" => Env::ip()
]));
if ($opt !== 1) {
    user_error("curl_setopt fail");
}

$res = curl_exec($ch);
if ($res === false) {
    user_error("curl_exec fail");
}
$code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);

if ($code !== 200) {
    error_log("google-recaptcha: " . $res);
    Shared::client_error("google recaptcha fail");
    exit();
}
$j = json_decode($res, true);
if (! $j["success"]) {
    Shared::client_error("google recaptcha invalid");
    exit();
}