Posting object from React.js to PHP using Axios

I am trying to create a login form using React JS as frontend and PHP as backend. I can't seem to figure out how to pass the form's data (email and password) to the PHP script. I tried googling and all the solutions either don't work for me or are out of data. I am using React v16.

This is my front-end code:

import React, { useState } from 'react';

// libraries
import { Col, 
          Button, 
          Form, 
          FormGroup, 
          Label, 
          Input} from 'reactstrap';
import Axios from 'axios'          


const App = () => {

  const [email, setEmail] = useState('')
  const [password, setPassword] = useState('')

  const submit = () => {
    Axios({
      method: 'POST',
      url: 'http://localhost:80/api/login.php',
      headers: {
        'Content-Type': 'application/json',
      },
      data: {
        email,
        password
      }
    })
    .then((response) => {
      console.log(response)
    })
    .catch((error) => {
      console.log(error)
    })
  }

  return (
    <div>

      <Form>
        <FormGroup row>
          <Label for="exampleEmail" sm={2}>Email</Label>
          <Col sm={10}>
            <Input value={email} onChange={e => setEmail(e.target.value)} type="email" name="email" placeholder="email" />
          </Col>
        </FormGroup>

        <FormGroup row>
          <Label for="examplePassword" sm={2}>Password</Label>
          <Col sm={10}>
            <Input value={password} onChange={e => setPassword(e.target.value)} type="password" name="password" placeholder="password" />
          </Col>
        </FormGroup>

        <FormGroup check row>
          <Col sm={{ size: 10, offset: 2 }}>
            <Button onClick={submit}>Submit</Button>
          </Col>
        </FormGroup>
      </Form>

    </div>
  );
}

export default App;

And this is my backend:

<?php

$data = json_decode(file_get_contents("php://input"));
echo "received data";
print_r("$data");

?>

For now, if I look at Chrome inspector, it will say Request Payload is {email: "xxx", password: "xxx"} so I know my front end is trying to send data to login.php but I don't know how to "catch" the data sent by the front end with PHP.

What I intended to do is: once login.php gets the data, it will return a JSON object of the data and the string "received data" back to the frontend.

Please help me take a look at this. I did research all day and still can't find a solution.

FYI, I have been trying every solution I can find online for example I tried this:

let data = {
      email,
      password
    }

let form = new FormData()
form.append('data', data)

Axios.post('http://localhost:80/api/login.php', form)
.then(...)
.catch(...)

and the backend will be:

$email = $_POST['email'];
$password = $_POST['password'];

But to no avail.