<?php
add_filter("gform_pre_render", "populate_dropdown");
add_filter("gform_admin_pre_render", "populate_dropdown");

function populate_dropdown($form){

    //only populating drop down for form id 122
    if($form["id"] != 122)
       return $form;


    //Creating campus drop down item array.
	$zip_code = $_POST["input_16"];
	$selected_campus = $_POST["input_2"];
	$selected_degree = $_POST["input_3"];

    $campus = get_campuses_by_zipcode($selected_campus, $zip_code);
	$degree = get_degrees($selected_campus, $selected_degree);


    foreach($form["fields"] as &$field){
		//Adding campuses to drop down (field id 2)
        if($field["id"] == 2){
            $field["choices"] = $campus;
        }

		//Adding degrees to drop down (field id 3)
		if($field["id"] == 3){
            $field["choices"] = $degree;
        }
	}
    return $form;
}

function get_campuses_by_zipcode($selected_campus, $zip_code){
	//Develop your logic here to get the list of available campuses.
	//Make sure to mark the selected item based on the $selected_campus variable
	$campuses = array();

	$campuses[] = array("text" => "Campus A", "value" => "Campus A", "isSelected" => true);
	return $campuses;
}

function get_degrees($selected_campus, $selected_degree){
	//Develop your logic here to get the list of available degrees based on the selected campus.
	//Make sure to mark the selected item based on the $selected_degree variable
	$degrees = array();

	$degrees[] = array("text" => "Degree A", "value" => "Degree A", "isSelected" => true);
	return $degrees;
}

?>