Global Variable within function

Hey, thanks for the quick reply! No, I shouldn't be trying to use it before it is defined. Here's the code:

//php section
import flash.net.URLLoader;
import flash.display.Loader;
import flash.events.*;
import flash.net.*;
import MyGlobal;

var images:XML;
var myRequest:URLRequest;
var myLoader:URLLoader;
// list of image urls that will come from loaded XML
MyGlobal.imageList;

myRequest = new URLRequest("Photography_1.php");
myLoader = new URLLoader();
myLoader.addEventListener(Event.COMPLETE, onFileLoaded);
// suggested handler for unexpected errors - avoids some headaches
myLoader.addEventListener(IOErrorEvent.IO_ERROR, onLoadError);
myLoader.load(myRequest);

// Note: all the listeners are removed
// it is always wise to remove listeners that are needed any longer
// to make objects eligible for arbage collection
function onLoadError(e:IOErrorEvent):void 
{
     trace(e.toString());
     myLoader.removeEventListener(Event.COMPLETE, onFileLoaded);
     myLoader.removeEventListener(IOErrorEvent.IO_ERROR, onLoadError);
}
          
function onFileLoaded(e:Event):void 
{
     trace ("File Loaded");
     myLoader.removeEventListener(Event.COMPLETE, onFileLoaded);
     myLoader.removeEventListener(IOErrorEvent.IO_ERROR, onLoadError);
      
     images = new XML(myLoader.data);
     // only now xml is ready and you can start loading images
      trace(images)
ParseImages(images);
}


function ParseImages(imageInput:XML):void{
     trace ("parsing images");
     MyGlobal.imageList = images.gallery.image;
     
     test_txt.text = (MyGlobal.imageList[0]);

//play movieclip
img_Loader.gotoAndPlay(1);
}

I'm defining the variable in function ParseImages and then using it within the img_Loader movie clip, which shouldn't even play until the end of that same function. The "text_txt.text = (MyGlobal.imageList[0];" outputs exactly what I want to access later in the movieclip so I know the value is being added. It just seems to disappear after the function ParseImages.

I had assumed it should work since it's global, but I'm not sure what the problem is. I'm new to classes and global variables in as3 so I could be doing something wrong; I'm just not sure what.