$(document).ready(function()
{
    var un = $("#username").value();
    var pw = $("password").value();

    $("a").click(function(){
        $.ajax({
            type: 'POST',
                        url: 'sifredegistir.php',
            data: '{ "username":"' + un + '", "password":"' + pw+ '" }',

                        success: function (result) {
                                alert(result.d);
                            }

        });
    });
});