Image Gallery Using Php Css And Javascript

I am trying to create a simple image gallery. I was following a tutorial on youtube. I am pretty sure i followed it well. However, I wasn't sure why it won't work. It seems that th

Solution 1:

Error in Id , it should be

document.getElementById("BigImage");

And second error

if (event.target.tagName == "IMG") {
   bigImage.src = event.target.src; //instead of bigImage.src = event.tagName.src;
 }

Fiddle