表达js和Php功能

I'm working on a project that uses expressjs, Php, Html and MongoDB

I have this code in my "Index.Html" File

<form action="/Login" method="POST">
  <input type="text" placeholder="name" name="Username">
  <input type="Password" placeholder="Password" name="Password">
  <button type="submit">Submit</button>
</form>

I have this code in my "Server.js" File (Expressjs)

app.post('/Login', (req, res) => {
   //to know that I really had recieve a data from my index.html 
   console.log(req.body)
   //to collect data from my database (MongoDB)
   db.collection('User').find(req.body,{Username:"",password:""}).toArray(function(err, results) {
   //show result from the database
   console.log(results)

    //The Question Starts here. 
  })
})

How can I send both of those data (req.body and result) to my php file? so I can Validate it. and also how can I send the data back from the PhP back to the server so the server could send the data back to the client?

You can use fetch to post a request to a php server. Example from the docs:

fetch('flowers.jpg')
.then(function(response) {
  return response.blob();
})
.then(function(myBlob) {
  var objectURL = URL.createObjectURL(myBlob);
  myImage.src = objectURL;
});