$conn = new mysqli("localhost","DB_USER","DB_PASS","DB_NAME");

<form method="POST">
<input name="email" placeholder="Email"><br>
<button>Send OTP</button>
</form>

<form method="POST">
<input name="email" placeholder="Email"><br>
<input name="otp" placeholder="OTP"><br>
<button>Login</button>
</form>