LoginForm

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Login</title>
</head>
<body>
    <form method="POST">
        Username: <input type="text" name="username"> <br>
        Password: <input type="password" name="password"> <br>
        <input type="submit" name="login">
    </form>
</body>
</html>
<?php
$users = ["John" => [ "password" => "123",
                      "email" => "john@abv.bg",
                      "birthday" => "12-01-1967",
                      "fullName" => "John Smith"
                     ],
          "Kiril" => ["password" => "321",
                    "email" => "kiril@abv.bg",
                    "birthday" => "27-03-1997",
                    "fullName" => "Kiril Kirilov"
                   ],
          "Martin" => ["password" => "456",
                       "email" => "martin@abv.bg",
                       "birthday" => "22-09-2000",
                       "fullName" => "Martin Angelov"
                ],
         ];

if (isset($_POST['login'])) {
    header("location: profile.php");
}