Game Register script Unity c sharp php

Register Script :-
==================
using UnityEngine;
using System.Collections;
using UnityEngine.UI;
using System.Text.RegularExpressions;
public class Register : MonoBehaviour {
    public InputField usernameInputField;
    public InputField EmailidInputField;
    public InputField PasswordInputField;
    public string username;
    public string emailid;
    public string password;
    public string ErrorString;
    public Text ErrorMsg;
    string register_url = "http://www.yourdomain.com/dr/Register1.php";
    public Image InternetCheckPanel;
    public Image RegisterSuccessfulPanel;
    public Text DidnotenterText;
    public Image LoginPanel;
    public Image RegisterPanel;
    public Button Join;
    public Text EmailErrorText;
    public Text UsernameErrorText;
    public Text RegisterCheckText;
    public string answer;


    void Start () {
        InternetCheckPanel.gameObject.SetActive (false);
        RegisterSuccessfulPanel.gameObject.SetActive (false);
    }

    public void JoinButton()
    {
        string UserEmail = EmailidInputField.text;
        string UserEntername = usernameInputField.text;
        if ((usernameInputField.text != "") && (EmailidInputField.text != "") && (PasswordInputField.text != "")) 
        {
            if((!IsValidUsername(UserEntername)) && (IsvalidEmailId(UserEmail)))
            {
                UsernameErrorText.text = "Username should be minimum 8 to 12 characters";
                EmailErrorText.text = "";
            }
            if((IsValidUsername(UserEntername)) && (!IsvalidEmailId(UserEmail)))
            {
                EmailErrorText.text = "Invalid Email Format";
                UsernameErrorText.text = "";
            }

            if((IsValidUsername(UserEntername)) && (IsvalidEmailId(UserEmail)))
            {
                StartCoroutine (StoreData ());
                EmailErrorText.text = "";
                UsernameErrorText.text = "";
                RegisterSuccessfulPanel.gameObject.SetActive(true);
                RegisterCheckText.text = "Loading.....";
            }
            
            if((!IsValidUsername(UserEntername)) && (!IsvalidEmailId(UserEmail)))
            {
                EmailErrorText.text = "Invalid Email Format";
                UsernameErrorText.text = "Username should be minimum 8 to 12 characters...";
            }
        }

        else
        {
            DidnotenterText.text = "Please fill above all fields";
        }
    }
    IEnumerator StoreData()
    {
        username = usernameInputField.text;
        emailid = EmailidInputField.text;
        password = PasswordInputField.text;
        WWWForm form = new WWWForm ();
        form.AddField ("username1", username);
        form.AddField ("emailid1", emailid);
        form.AddField ("password1", password);
        
        WWW download = new WWW( register_url, form );
        yield return download;
        answer = download.text.ToString ();

        if (answer == "Successfully Registered") {
            RegisterCheckText.text = "Successfully Registered";
        } 
        else 
        {
            RegisterCheckText.text = "Username or Email Already Existed";
        }
        if (!string.IsNullOrEmpty (download.error)) {
            print ("Error downloading: " + download.error);
            ErrorString = download.error;
            ErrorMsg.text = ErrorString;
        } 
        else {

        }
    }

    public void OkButton()
    {
        if (RegisterCheckText.text == "Successfully Registered") {
            Time.timeScale = 1;
            InternetCheckPanel.gameObject.SetActive (false);
            RegisterSuccessfulPanel.gameObject.SetActive (false);
            RegisterPanel.gameObject.SetActive (false);
            LoginPanel.gameObject.SetActive (true);
            usernameInputField.text = "";
            PasswordInputField.text = "";
            EmailidInputField.text = "";
            Join.interactable = false;
            usernameInputField.interactable = true;
            EmailidInputField.interactable = true;
            PasswordInputField.interactable = true;
            Join.interactable = true;
        } else 
            if(RegisterCheckText.text == "Username or Email Already Existed")
        {
            RegisterSuccessfulPanel.gameObject.SetActive (false);
        }
    }

    public static bool IsvalidEmailId(string InputEmail)
    {
        Regex regex = new Regex(@"^([\w\.\-]+)@([\w\-]+)((\.(\w){2,5})+)$");
        Match match = regex.Match (InputEmail);
        if (match.Success)
            return true;
        else
            return false;
    }
    public static bool IsValidUsername(string InputUsername)
    {
        Regex regex1 = new Regex("^[a-zA-Z]{8,12}$");
        Match match1 = regex1.Match (InputUsername);
        if (match1.Success)
            return true;
        else
            return false;
    }
    public void BackButton()
    {
        RegisterPanel.gameObject.SetActive (false);
        LoginPanel.gameObject.SetActive (true);
    }

}



Server Side Script :-
======================
<?php 
$servername = "Your_ServerName"; 
$username = "Your_UserName";
$password = "************";
$dbname = "Your_DB_Name";


$conn = new mysqli($servername, $username, $password, $dbname); 


if ($conn->connect_error) { 
    die("Connection failed: " . $conn->connect_error); 
} 
$exits = 0; 

$Username2=$_POST['username1'];
$Emailid2 = $_POST['emailid1'];
$Password2 = $_POST['password1'];

$query = "SELECT * FROM userinfo where username = '$Username2' OR emailid = '$Emailid2'";
$result = mysqli_query($conn,$query);
$num = mysqli_num_rows($result);

if($num == 0)
{
    $sql = "INSERT INTO userinfo (username,emailid,password) VALUES ('$Username2','$Emailid2','$Password2')";
    $result1 = mysqli_query($conn,$sql);
    echo "Successfully Registered";
}
else
{
    echo "Username already existed" ;
}
    
mysqli_close($conn);

?>