Adding User Id to Session

Suppose that in addition to the authorization mark, we would also like to write his id to the session.

In this case, we can get it using the function mysqli_insert_id. This function gets the id of the last record inserted in this script, which is exactly what we need.

Let's implement it:

register.php<?php
  if (!empty($_POST['login']) and !empty($_POST['password'])) {
    $login = $_POST['login'];
    $password = $_POST['password'];
    
    $query = "INSERT INTO users SET login='$login', password='$password'";
    mysqli_query($link, $query);
    
    $_SESSION['auth'] = true;
    
    $id = mysqli_insert_id($link);
    $_SESSION['id'] = $id; // writing id to the session
  }
?>