php，未定义变量和全局变量

Question

1. 变量otp_1是否在if块下无法访问？

   我尝试将otp_1设置为全局变量，但不起作用。

    if (array_key_exists('number', $_POST)) {
   $url = "https://www.way2sms.com/api/v1/sendCampaign";
   $otp_1 =  generateNumericOTP();
   $message_to_send =  "Your OTP  is : " . $otp_1;
   $message = urlencode($message_to_send);
   $number = $_POST['number'];
   $num = urlencode($number);
   $curl = curl_init();
   curl_setopt($curl, CURLOPT_POST, 1);
   curl_setopt($curl, CURLOPT_POSTFIELDS, "apikey=&secret=GUJQRCYVZRE05SC&usetype=stage&phone=$num&senderid=sanketmagar2001@gmail.com&message=$message");
   curl_setopt($curl, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
   curl_setopt($curl, CURLOPT_URL, $url);
   curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
   $result = curl_exec($curl);
   curl_close($curl);
   $res = explode('status":"', $result);
   $res_ = explode('"}', $res[1]);
   $final_msg = $res_[0];
   if ($final_msg == "success") {
       echo "<div class='alert alert-success'>OTP send Successfully ! </div>";
   } else {
       echo "<div class='alert alert-danger'>couldn' Send OTP ,plz try Later !</div>";
   } }    if(array_key_exists('otp',$_POST)) {
   echo $otp_1; }
   

   注意：未定义的变量：otp_1在C：\ xampp \ htdocs \ action.php中 第130行