JQUERY AJAX .get can't access .php file on new server -

recently had website move new server. working. now, of $().get("whatever.php") fail. doesn't make php script @ now.

for example:

index.html

$.get("test.php", function(data){     alert(data); }).fail(function(data){console.log(data)}); 

test.php

<?php     echo "haii"; ?> 

the fail function logs:

object { readystate: 4, getresponseheader: .ajax/v.getresponseheader(), getallresponseheaders: .ajax/v.getallresponseheaders(), setrequestheader: .ajax/v.setrequestheader(), overridemimetype: .ajax/v.overridemimetype(), statuscode: .ajax/v.statuscode(), abort: .ajax/v.abort(), state: .deferred/d.state(), always: .deferred/d.always(), then: .deferred/d.then()} 

alternatively, following still works (.get html):

$.get("test.html", function(data){     alert(data); }).fail(function(data){console.log(data)}); 

the new server virtual private, unsure if potentially impact this?

lastly, of these ajax calls within same domain folder.

any assistance appreciated.

update:

attempting open test.php on server results in 500 internal server error.

500 internal server means file doesn't have permissions execute, , problem ajax not working either. chmod file 644 , (it 666 right now)