Anyone know how to call this ph page from a path other than root?

Wondering if anyone has found a way to call these php pages from somewhere other than root folder? tried about everything i can think of cant find a way.

from this article javascript:

https://asprunner.com/forums/topic/22701-custom-dependent-dropdown-boxes

var func = function(e){

$.post("mylookup.php", { <------------------looking for a way to call this from folder other than the web root? example ./include/mylookup.php or https://myserver/myfolder/lookup.php etc

'category' : this.getValue() },

function(data) {

.......