data.json

{
    "url": "http://idp.debian.local/login/",
    "page": "http://idp.debian.local/manage/users/",
    "username_id": "#id_username",
    "username_value": "root",
    "password_id": "#id_password",
    "password_value": "root"
}

do_login.js

var system = require('system');
var page = require('webpage').create();

function json_dump(data){
    console.log(JSON.stringify(data));
}

input = JSON.parse(system.stdin.read(2000));

page.open(input.url, function(status){
    if (status !== 'success'){
        console.log(JSON.stringify({'result':status}));
        phantom.exit(1);
    }
    
    page.injectJs('jquery.min.js');

    page.onLoadFinished = function(){
        page.render('login.png');
        console.log(JSON.stringify({'result': status, 'cookies': page.cookies}));
        phantom.exit(0);
    }

    page.evaluate(function(input ){

        if ($(input.username_id).length == 0){
            console.log(JSON.stringify({'result': 'ok'}));
        }

        $(input.username_id).val(input.username_value);
        $(input.password_id).val(input.password_value);
        $(input.username_id).parents('form').find('input[type=submit]').click();
    }, input);
});

get_page_content.js

var system = require('system');
var page = require('webpage').create();

function json_dump(data){
    console.log(JSON.stringify(data));
}

input = JSON.parse(system.stdin.read(2000));

page.open(input.page, function(status){
    if (status !== 'success'){
        console.log(JSON.stringify({'result':status}));
        phantom.exit(1);
    }
    page.render('page.png');
    console.log(JSON.stringify({'result':'ok', 'cookies': page.cookies, 'content': page.content}));
    phantom.exit();
});

login.png

page.png