<?php

class User
{
    private $username;
    private $password;

    public function __construct($username, $password)
    {
        $this->username = $username;
        $this->password = $password;

    }


    function login()
    {
        $result = mysql_query("
            SELECT username, password
            FROM users
            WHERE username='{$this->username}' AND password='{$this->password}'
        ";
        if ($result)) {
            return mysql_num_rows($result);
        }
        return false;
    }
}

$user = new User($_POST['username'], $_POST['password']);
if ($user->login()) {
    echo "User can login";
} else {
    echo "User not found";
}