Android工作室不与php脚本交谈并且没有错误

Previously, I had 3 scripts that needed work, here. I did what the kind gents told me to do, and changed the siss to ssi (string,string,int(boolean)). I changed the localhost to ip-address:3306. And Android Studio STILL won't send anything to the db. here are the scripts:

create user script

createuser.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                final String username = username1.getText().toString();
                final String password = password1.getText().toString();
                final String isadmin = isAdmin.getText().toString();
                Response.Listener<String> responseListener = new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        try {
                            JSONObject jsonResponse = new JSONObject(response);
                            boolean success = jsonResponse.getBoolean("success");
                            if (success){
                                Intent intent = new Intent(CreateUser.this, MainActivity.class);
                                CreateUser.this.startActivity(intent);
                            }else{
                                AlertDialog.Builder builder = new AlertDialog.Builder(CreateUser.this);
                                builder.setMessage("Register Failed")
                                        .setNegativeButton("Retry",null)
                                        .create()
                                        .show();


                            }
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                };
                RegisterRequest registerRequest = new RegisterRequest(username,password,isadmin,responseListener);
                RequestQueue queue = Volley.newRequestQueue(CreateUser.this);
                queue.add(registerRequest);
            }
        });

register request

public class RegisterRequest extends StringRequest {

    private static final String REGISTER_REQUEST_URL = "http://192.168.6.104:3306/phptesting/Register.php";
    private Map<String, String> params;
    public RegisterRequest(String username, String password,String isAdmin, Response.Listener<String> listener){
        super(Method.POST, REGISTER_REQUEST_URL,listener,null);
        params = new HashMap<>();
        params.put("username",username);
        params.put("password",password);
        params.put("isAdmin",isAdmin+"");
    }

    public Map<String, String> getparams() {
        return params;
    }
}

and my php script

    <?php
    $db_host = 'localhost:3306';
    $db_user = 'root';
    $db_pass = '';
    $db_name = 'test';

    $con = mysqli_connect($db_host,'user',$db_pass,$db_name);
    if($con){
        echo "connection successful";
    }
    if (mysqli_connect_errno()) {
    printf("Connect failed: %s
", mysqli_connect_error());
    exit();
    }

    $isAdmin = $_POST["isAdmin"];
    $username = $_POST["username"];
    $password = $_POST["password"];
    if ($isAdmin = null){
        $isAdmin = 0;
    }
    if ($username = null){
        $username = "fakename";
    }
    if ($password = null){
        $password = "fakepassword";
    }
    $statement = mysqli_prepare($con, "INSERT INTO user (username,password,isAdmin) VALUES (?, ?, ?)");
    mysqli_stmt_bind_param($statement,'ssi',$username,$password,$isAdmin);
    mysqli_stmt_execute($statement);

    $response = array();
    $response["success"] = true;  

    echo json_encode($response);
?>

I get no app-crashing error in logcat or run. Is there a filter i need to put on logcat to see the php/mySQL error? Thanks in advance