谷歌重新收回缺失的输入回应

I have an error with the response of Google recaptcha. Please, could you help me to find my error ?

function captcha(){
    $secret = "...";
    $response = $_POST['g-recaptcha-response'];
    $remoteip = $_SERVER['REMOTE_ADDR'];
    $api_url = "https://www.google.com/recaptcha/api/siteverify?secret=".$secret."&response=".$response."&remoteip=".$remoteip;
    $decode = json_decode(file_get_contents($api_url), true);
    if ($decode['success'] == true) {
        return $decode['success'];
    }else{
        $errorsCode = "";
        foreach ($decode['error-codes'] as $key => $value) {
            $errorsCode .= '<p><strong>' . $key.':</strong> '.$value.'</p>';
        }
        return $errorsCode;
    }
}

I get always the same error : missing-input-response.

Thank you for your help !

EDIT : Solved with https://gist.github.com/jonathanstark/dfb30bdfb522318fc819 by Mrpink