从Web服务获取访问令牌

Question

我通过硬编码访问令牌从Web服务获取数据，但是当我尝试使用curl获取访问代码时，它不会

这是api给出的代码

curl -k -d "grant_type=password&username=Username&password=Password" \
        -H "Authorization: Basic SUpfTjFmTlo1UmZLS0VrYVBFVUtOUXJZcHFjYTpiRU1NNE9ITmxJYUlSXzNaUTA4akhSMnV0UkVh" \
         https://api.lankagate.gov.lk:8243/token

这是我的代码

function get_exam_mode_of_study() {

        $URL = "test_url";
        $ch = curl_init($URL);


        curl_setopt($ch, CURLOPT_HTTPHEADER, array(
            'Authorization: Basic SUpfTjFmTlo1UmZLS0VrYVBFVUtOUXJZcHFjYTpiRU1NNE9ITmxJYUlSXzNaUTA4akhSMnV0UkVh',
            'Content-Type: application/x-www-form-urlencoded'

        ));
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
        curl_setopt($ch, CURLOPT_POST, 1);
//        curl_setopt($ch, CURLOPT_HTTPHEADER, array());
        curl_setopt($ch, CURLOPT_POSTFIELDS, array(
            'grant_type: password',
            'username: pass',
            'password: user'
        ));
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        $output = curl_exec($ch);
        print_r($output);
        exit;
        curl_close($ch);
//        }
    }

我该怎么做