Reactjs Api Call Not working in Yii2 - reactjs

Question

I'm new to React js And I using Yii2 as my backend..! When I Send a API request to yii2 ,It Returns me the 500 Error.I don't know,Where I made a mistake.
Here is my React Js Code for API call,
fetch('localhost/learning-react/api/admin/signup', {
method: 'POST',
headers: {
'Accept': 'application/json',
'Content-Type': 'application/json'
},
body: JSON.stringify({
fname:fname,
lname:lname,
email:email,
uname:uname,
passwd:passwd
})
}).then((response) => response.json())
.then((responseJson) => {
if(responseJson['status']==='1')
{
alert(responseJson['msg']);
}
}
And This is My Yii2 Backend code,
public function actionSignup()
{
//$model = new TblUsers();
return "success";
}
Sorry For my Inability to finding mistakes in my code..!

Answer 1

First of all, 500 means generic server error. So you will need to post your error log as per my comment to help on that. However, I have found your code on the backend is wrong. You do not user restful controller in your code and as such it is not a REST API at all. So I advice you to read through Restful APIs in the Guide. That being said, you basically need to:
Create Restful controller by inheriting from yii\rest\Controller.
Return either Array, DataProvider or instance of yii\base\Model to have guarantee of automated serialization to JSON
so I will show you a simple example to give you an idea. Please read the guide to get in-depth insights on REST API with Yii2.
<?php
namespace app\modules\v1\controllers;
use yii\rest\Controller;
class LoginController extends Controller
{
public function actionSignup()
{
$model = new TblUsers();
//register a user
//return registred user
return [
'success' => true,
'member' => $model;
];
}
}

Answer 2

Let try the following, it may help.
You are making a rest post request, this means two things, first info will travel by POST request, and second dont forget its rest.
try opening the url in the browser, unless you define a rule it should open.
So go ahead open: http://localhost/learning-react/api/admin/signup you should see a "success" on the screen, or you will se the full 500 error printed.
If you were able to open the url on the browser, try the call again, and check your chrome debugger on the network tab. Look for the 500 error open it and read the error, it should be fully printed there on the response tab i.e.
when this is solved, don't forget to enable rules to allow only POST as request, and add the appropriate format for the response so you can consume it as json.
Yii::$app->response->format = Response::FORMAT_JSON;
Hope it helps debuggin.