curl --location --request POST 'https://api.4321.sh/sms/variable' \
--header 'Content-Type: application/json' \
--data-raw '{
    "apikey": "string",
    "secret": "string",
    "sign_id": "string",
    "content": "string",
    "ext_no": "string",
    "send_time": "string"
}'{
    "code": 0,
    "msg": "OK",
    "msg_no": "2016072909264497197473179",
    "count": 1
}