登录后使用Javascript获取文件

Question

I want to run a javascript which gets a .php file from another Server, which is secured with a login. I have the full login data and right to use the code.

So my question is, how can javascript automatically login to this website and then run the code? Do I need an extra PHP-File?

Downloading the file from the other server isn´t an option for me.

My example code:

$.get('http://domain.com/file.php',  function(data) {
    if(CODE) {
        CODE
    } else {
        CODE
    }