User Registration and login operations Immediately after that

Question

I want to implement a php file that can to do the User Registration and login operations Immediately after that.

I think the code structure should be as follows:

Registration and login.php

<?php
session_start();
if($_SERVER["REQUEST_METHOD"] == "POST") {
$username = $_POST['username'];
$password = $_POST['password'];
//Check the fields.If they are correct
//Check if the username exists and password is correct
$_SESSION['login_user']=$username;
//Go to the profile.php.
//But if the username does not exists, insert the username and password in table}

else {mysql_close($connection);}

Can the code above work well and is it a good answer for my question?

Answer 1

That is also a good approach ...

first check if user with that username/email already exists

If exists, then match username and password, and create session for that user

If not, then create the user and then create a session (that means user is logged in too) for that user right there