Php call

<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>Login 3</title>
</head>
	<body>
		<?php
			session_start();
			if($_SESSION['userid']>0){
				echo "<a href='logout.php'>Выход</a>";

			}
			else{
				if(($_POST['username'] == '') or ($_POST['password'] == '')){
					echo "
						<form action='./login3.php' method='post'>
							Логин: <input type='text' name='username'><br>
							Пароль: <input type='text' name='password'><br>
							<input type='submit' name='submite' value='Войти'>
						</form>
					";
				}
				else{
					$username = $_POST['username'];
					$userpass = $_POST['password'];

					require_once 'connect.php';

					$sql = "SELECT * FROM users WHERE login='$username' and password='$userpass' ";

					$result = $link -> query($sql);
					$row = $result -> fetch_assoc();

						if($row){
							echo "Добро пожаловать ", $row['login'], "<br>", "Ваш id ", $row['id'];
							$_SESSION['userid'] = $row['id'];
						}
						else{
							echo "Вы неправильно ввели имя пользователя или пароль", "<br>", "<a href='login3.php'>Вренуться</a>";

						}

					$result->close();
					$link->close();

				}
			}

		?>
	</body>
</html>