Интеграция OTP при регистрации

У меня возникают проблемы при интеграции функции «отправить OTP» в мою регистрационную форму. Мне дали API от поставщика SMS, но я не знаю, как интегрировать его в мою форму. Мне нужно, чтобы пользовательские данные были записаны в моей базе данных после проверки OTP. Но как работает процесс проверки? и как система будет генерировать 6-значный случайный код для пользователя? Я пробовал другой метод и поиск в Интернете, но ничего из этого не работает. Кто-нибудь может помочь?

Вот моя форма:

            <div class="modal-body">
<form action="includes/signup.inc.php" method="POST" class="p-3">
<div class="form-group">
<label for="recipient-name" class="col-form-label">First Name</label>
<input type="text" class="form-control" placeholder="First Name" name="first" required="">
</div>
<div class="form-group">
<label for="recipient-name" class="col-form-label">Last Name</label>
<input type="text" class="form-control" placeholder="Last Name" name="last" required="">
</div>
<div class="form-group">
<label for="recipient-name" class="col-form-label">Username</label>
<input type="text" class="form-control" placeholder="Username" name="uid" required="" >
</div>
<div class="form-group">
<label for="recipient-name1" class="col-form-label">Date of Birth</label>
<input type="date" class="form-control" placeholder="dob" name="dob" required="">
</div>
<div class="form-group">
<label for="recipient-name" class="col-form-label">Email Address</label>
<input type="email" class="form-control" placeholder="Email" name="email" required="" >
</div>

<div class="form-group">
<label for="recipient-name" class="col-form-label">Password</label>
<input type="password" class="form-control" placeholder="Password" name="pass" required="">
</div>
<div class="form-group">
<label for="recipient-name" class="col-form-label">Confirm Password</label>
<input type="password" class="form-control" placeholder="Confirm Password" name="c_pass" required="">
</div>
<div class="form-group">
<label for="recipient-name" class="col-form-label">Are You Previously an  Existing Member?</label>
<select class="form-control" id="recipient-name10" name="member">
<option>Yes</option>
<option>No</option>
</select>
</div>
<div class="form-group">
<label for="recipient-name" class="col-form-label">Where do you know about this membership?</label>
<select class="form-control" id="recipient-name11" name="outlet">
<option>The Metallic Kitchen @ Golden Triangle Pelangi, JB</option>
<option>The Metallic Kitchen @ Taman Mount Austin, JB</option>
<option>The Metallic Kitchen & Bar @ Setapak Village, KL</option>
<option>None of the above</option>
</select>
</div>
<div class="form-group">
<label for="recipient-name" class="col-form-label">OTP</label>
<input type="text" class="form-control" placeholder="OTP" name="otp" required="">
</div>
<div class="right-w3l mt-4 mb-3">
<input type="submit" class="form-control" value="Create account" name="submit">
</div>
</form>

</div>

и вот мой API провайдера смс:

<?php
function sendSmsToEsms() {
$url = 'https://api.esms.com.my/sms/send';

// replace yourusername, yourpassword, and 60123456789 to suits your need
$data = array('user' => 'yourusername',
'pass' => 'yourpassword',
'to' => '60123456789',
'msg' => 'RM0.00 Hello from ESMS');

$options = array(
'http' => array(
'header'  => "Content-type: application/x-www-form-urlencoded; charset=utf-8",
'method'  => 'POST',
'content' => http_build_query($data)
)
);
$context  = stream_context_create($options);
$result = file_get_contents($url, false, $context);
if ($result === FALSE) { /* Handle error */ }

var_dump($result);
}
?>

Вот мой код для добавления данных в базу данных:

<?php

if (isset($_POST['submit'])){

include_once 'db.php';

$first = mysqli_real_escape_string($conn,$_POST['first']);
$last = mysqli_real_escape_string($conn,$_POST['last']);
$uid = mysqli_real_escape_string($conn,$_POST['uid']);
$dob = mysqli_real_escape_string($conn,$_POST['dob']);
$email = mysqli_real_escape_string($conn,$_POST['email']);
$mobile = mysqli_real_escape_string($conn, $_POST['m_number']);
$pwd = mysqli_real_escape_string($conn,$_POST['pass']);
$member =mysqli_real_escape_string($conn, $_POST['member']);
$outlet = mysqli_real_escape_string($conn,$_POST['outlet']);

//ERROR HANDLERS
//CHECK FOR EMPTY FIELDS
//if(empty($first)||empty($last)||empty($uid)||empty($dob)||empty($email)||empty($mobile)||empty($pwd)||empty($member)||empty($outlet))
//{
//header("Location:../index.php?signup=empty");
//exit();
//}else{
//check if input characters are valid
//if(!preg_match("/^[a-zA-Z]*$/", $first)|| !preg_match("/^[a-zA-Z]*$/", $last)){
//header("Location:../signup.php?signup=invalid");
//exit();
//}else{
//check email
if(!filter_var($email,FILTER_VALIDATE_EMAIL)){
echo "<script>alert('Invalid Email,please register again.')</script>";
echo "<script>window.open('../index.php','_self')</script>";
exit();
}else{
//check if username is same
$sql = "SELECT * FROM users WHERE user_uid = '$uid'";
$result = mysqli_query ($conn,$sql);
$resultCheck = mysqli_num_rows ($result);

if ($resultCheck > 0) {
echo "<script>alert('Username has been taken, please register again.')</script>";
echo "<script>window.open('../index.php','_self')</script>";
exit();
}else{
//Hashing pwd
$hashedPwd = password_hash($pwd,PASSWORD_DEFAULT);
//INSERT THE USER INTO THE DATABASE
$sql = "INSERT INTO users (user_first,user_last,user_uid,user_dob,user_email,user_mobile,user_pwd,user_member,user_outlet) VALUES ('$first','$last','$uid','$dob','$email','$mobile','$hashedPwd','$member','$outlet');";
mysqli_query($conn,$sql);
echo "<script>alert('You have been Registered Successfully, Please login from our main page')</script>";
echo "<script>window.open('../index.php','_self')</script>";
exit();

}
}
}



else{
header("Location:../index.php");
exit();
}


?>