Question

I have write this code but it does work only if I am already logged in facebook, otherwise appears a popup window that require me email and password to login in facebook.

This is the code:

window.fbAsyncInit = function () {
    FB.init({
        appId: 'xxx',
        frictionlessRequests: true,
        status: true,
        cookie: true,
        xfbml: true,
        oauth: true
    });

    function update(response) {
        if (response.authResponse) {
            FB.api('/me', function (info) {
                login(response, info);
            });

        } else {

        }
    }

    FB.getLoginStatus(update);
};
(function () {
    var e = document.createElement('script');
    e.async = true;
    e.src = document.location.protocol + '//connect.facebook.net/en_US/all.js';
    document.getElementById('fb-root').appendChild(e);
}());


function login(response, info) {
    if (response.authResponse) {
        publish();
    }
}

function publish() {
    var publish = {
        method: 'feed',
        access_token: '<?php echo $token; ?>',
        message: 'How are you ?',
        name: 'hi friends',
        caption: 'yuhuuuuuuuu',
        description: (' '),
        link: 'http://www.example.com',
        picture: 'http://cdn1.hark.com/images/000/004/514/4514/original.jpg',
        actions: [{
            name: 'Hello',
            link: 'http://www.example.com/'
        }],
        user_message_prompt: 'Share on facebook'
    };

    FB.ui(
    publish, function (response) {
        if (response && response.post_id) {
            alert('Post was published.');

        } else {
            alert('Post was not published.');
        }
    });
}

Answer 1

In your update method, in the blank else you should call the FB.login method:

Calling FB.login prompts the user to authenticate your application
using the OAuth Dialog.

However, you can’t just do this:

function update(response) {
    if (response.authResponse) {
        FB.api('/me', function (info) {
        login(response, info);
        });

    } else {
        FB.login(function(response) {
            if (response.authResponse) {
                console.log("user is logged in!", response.authResponse);
            }
        });
    }
}

Since as it states in the documentation:

Calling FB.login results in the JS SDK attempting to open a popup
window. As such, this method should only be called after a user click
event, otherwise the popup window will be blocked by most browsers.

You’ll have to show a user a button or something that tells him to click in order to login, and then you can call the FB.login method.