WordPress functions can't run within content loaded using AJAX

Hello,

I’ve been trying to solve this problem for a few hours now, so any help would be greatly appreciated!!

I wrote an AJAX function to load two different pages that toggled using 2 links. Each of these pages includes native wordpress functions like get_current_user_id(). They work fine if I load them normally by entering in the address in the address bar, but when I call the page using ajax, I receive a fatal error of an undefined function.

I’ve done a lot of searching for this on the web already, and it seems like everybody refers to the AJAX in Plugins page, which tells me to use add_action(‘wp_ajax…’,’…’). I’ve sunk many hours into trying to implement this with no success. Can anyone give me some pointers?

Thanks,
Ben

Here’s my code:

HTML:

<ul id='learn-selector'>
        <h2>QUIZZES</h2>
        <li class='quiz-new'><a href='?learn=quiz-overview'>New Quiz</a></li>
        <li class='quiz-clinic-settings'><a href='?learn=quiz-error'>Settings</a></li>
    </ul>
<div id='learn-body'>
<?php
     if (isset($_GET['learn'])){
          switch ($_GET['learn']){
              case 'quiz-overview':
                   include 'quiz-overview.php';
              break;
              case 'quiz-error':
                   include 'quiz-error.php';
              break;
          }
     }
?>
</div> <!-- learn-body-->

Javascript:

function getHTTPObject() {
	var xhr = false;
	if (window.XMLHttpRequest){
			xhr = new XMLHttpRequest();
	}
	else if (window.ActiveXObject){
		try{
			xhr = new ActiveXObject('Msxml2.XMLHTTP');
		}
		catch(e){
			try{
				xhr = new ActiveXObject('Microsoft.XMLHTTP');
			}
			catch(e){
				xhr = false;
			}
		}
	}
return xhr;
}
function grabFile(file){
	var request = getHTTPObject();
	if (request){
		request.onreadystatechange = function (){
		parseResponse(request);
		};
	request.open('GET',file,true);
	request.send(null);
	return true;
	}
	else {
		return false;
	}
}
window.onload = prepareLinks;
function prepareLinks(){
	if (!document.getElementById || !document.getElementsByTagName){
		return;
	}
	var list = document.getElementById('learn-selector');
	var links = list.getElementsByTagName('a');

	for (var i=0; i<links.length;i++){
		links[i].onclick=function(){
			var query = this.getAttribute('href').split('?learn=')[1];
			var url ='https://eyeguru.org/wp-content/themes/thesis_185/custom/'+query+'.php';
			return !grabFile(url);
		};
	}
}
function parseResponse(request){
	if (request.readyState ==4){
		if(request.status == 200 || request.status == 304){
			var details = document.getElementById('learn-body');
			details.innerHTML = request.responseText;
		}
	}
}